In early 2011, Ginger Chien sat at her desk at AT&T’s Redmond, Washington office, scrolling through AT&T’s online document library. She doesn’t quite remember what she was looking for. It was something starting with a T.

“It would’ve either been information about AT&T stock T , since its ticker is T, or it would’ve been this internal collaboration system that we use. It was very routine business stuff,” says Chien, who is a device applications architect at AT&T and has worked for the company for 19 years.

While thumbing through the documents, one entry caught her attention: AT&T’s transgender guidelines.

The 19-page document laid out how an employee would transition genders while on the job, including the steps required to change his or her name. For Chien, 52, who had been presenting as a woman everywhere but at the office for the past five years, it was also a life-changer.

AT&T introduced its transition guidelines in late 2010 at the suggestion of its LGBT employee resource group called League. And AT&T is not alone.

For more than a decade, some of the nation’s largest companies have stepped in where the United States government has not by providing nondiscrimination protections, healthcare benefits, and transition guidelines to their transgender employees, even as the community remained marginalized in mainstream American culture.

According to the 2015 Human Rights Campaign’s Corporate Equality Index, which rates American workplaces on LGBT equality, 66% of Fortune 500 companies have instituted a gender identity non-discrimination policy, up from 3% in 2002, when the index was launched. One-third of Fortune 500 companies offer transgender-inclusive healthcare coverage, up from zero in 2002.

Transgender people are currently experiencing a cultural moment in the sun. The July issue of Vanity Fair that showed the first-ever photo of Caitlyn Jenner presenting as a woman—posing coyly in a white satin bustier—marked the latest milestone in what might be considered the transgender community’s long-awaited and ongoing coming of age.

Television series like Amazon’s “Transparent,” which focuses on a family whose father is transgender, and Netflix’s “Orange is the New Black,” which features transgender actress Laverne Cox, have also boosted transgender individuals’ prominence in popular culture.

While a transgender cultural awakening is in full form today, Corporate America, it seems, took notice of the community—and took action to embrace it—much earlier. Like AT&T, other large companies have adopted specific gender transition guidelines. The Human Rights Campaign began to keep track of such policies in its 2006 index. And the use of transition guidelines is one of eight practices that count towards meeting the index’s “organizational LGBT competency” criteria. Of the eight practices, companies must exhibit at least three to be considered for the Index’s perfect 100 score. In 2008, 90 companies offered transitioning guidelines. This year, that total grew to 291. Of all Fortune 500 companies, 54 had gender transition guidelines in 2008; 140 have them this year.

“We’ve seen the number of gender identity protections balloon over the past few years,” says Liz Cooper, associate director of corporate equality programs for the HRC. The implementation of transition guidelines “speak[s] volumes as to how much companies are prioritizing [the transitioning] experience. They’re not just … adopting inclusive policies; they want to translate those policies into practices.”

Chien, a Seattle native, says she was aware of her female gender identity from a very young age, but “there was no space within my Chinese community or what was a pretty conservative American culture at the time … for me to consider doing anything different from what the culture expected of me.”

After seeking help from the Ingersoll Gender Center in Seattle more than a decade-and-a-half ago, Chien began to present as a woman on occasion in her personal life, but never at work.

She knew of transgender friends who had come out at work; their experiences ranged from “absolutely outstanding,” Chien says, to “absolutely awful,” with some leading to harassment and even termination. Chien says she worried about where her experience would land on that spectrum. “Given the large number of people I work with—teams of engineers from foreign countries—and the public speaking engagements on technical subjects that I do on behalf of the company … my fear was that that might get dialed back.”

Chien’s worries eased when, by pure accident, she discovered AT&T had guidelines on the matter. “The power of a bureaucratic form is hard to understate,” she says.

Chien recalls filling out the paperwork to record her gender change with AT&T. The form asked for the reason for the change. There were two options. “The first was data entry error. The second reason was employee choice,” she says. “All of the uncertainty, the randomness and chaos that I’d seen in the outside world…was very, very quickly erased by this simple check box—it’s the employee’s choice.”

Overall, the process was straightforward, Chien says. It involved a gender change request and a name change request. Chien also updated the gender on her government IDs, which in the state of Washington and at the federal level required a doctor’s declaration of “appropriate treatment.”

After getting those basics worked out, Chien also needed to tell her manager about her transition.

At that point, Chien was one year into her hormone treatment, but she wore baggy pants and shirts to hide the changes. She was undergoing hair removal. For many years, she had worn her hair in a long ponytail and had studs in her pierced ears. That look, Chien says, “[isn’t] remarkable in an engineering [or] computing setting.” She adds: “My intent was to give no obvious indication of gender change.”

Her boss Mike Dunn, director of device development in applications, received a call from Chien at his home—the first time she’d ever contacted him outside of work, he says. It caught Dunn by surprise. “My only reaction was, ‘This has to be a big weight lifted for you. Thank you for trusting me with this process. I’ll help you in any way I can,’” he told Fortune.

Laverne Cox, featured in Netflix's "Orange is the New Black" Laverne Cox, featured in Netflix’s “Orange is the New Black”Courtesy of Netflix

Together, they worked out a transition schedule and notified managers further up the chain. In August 2011, Dunn sent a matter-of-fact email to around two dozen managers whose teams work with Chien. “It said, ‘On this date, the employee you work with is going to transition on the job, and she will go by the name Ginger and we expect that professionalism will continue to be the norm.’” Chien recalls. “It was no different than someone getting married; no different than someone having a baby.”

At a meeting the next day, she finally told her team about her transition face-to-face. “I think my coworkers were mostly or fully caught off guard,” she says. They responded “professionally,” Chien says. “There were a few heartwarming encounters that I had with people in private. One person hung around after the meeting and was actually very tearful and sympathetic. Someone else told me, ‘I wish I had your courage.'”

Chien immediately began using the women’s restroom since AT&T’s policy says that employees are to be granted unrestricted use of restrooms that correspond to their full-time gender presentation.

Chien told her coworkers about her transition on a Friday and she wore her “typical” Dockers, a baggy cotton shirt, hair in a ponytail, and her “masculine” glasses. The plan was for her to work from home for a week to help her coworkers adjust and allow them to ask questions of her supervisor without fear of offending Chien. She returned the next Friday, when her team had a long-scheduled summer picnic. Chien attended the picnic in a tank top, a mid-length cotton skirt, sandals, and her “feminine glasses.” The picnic “turned out to be a good neutral-ground, informal place to reintroduce myself,” Chien says.

A slow, painful evolution

Corporate America’s acceptance of the transgender community has been a slow evolution that’s played out over several decades. Back in the 1960s and 1970s, the rare instances of gender reassignment surgery almost always triggered a change in a transgender patient’s profession, say Janis Walworth of the Center on Gender Sanity and author of Transsexual Workers: An Employer’s Guide and Working with a Transsexual. If a person was transitioning from male to female, she would have to quit an engineer job and become a file clerk, which would mean a huge loss of income at a time when the person needed it the most, Walworth says.

Back then, psychiatrists who signed off on gender reassignment surgery insisted that candidates prove that they could support themselves in their new gender role. And since many jobs were gender-specific in that era, a job change was mandatory. Plus, there was a pervasive assumption that employees couldn’t transition and keep their job, Walworth says, which was largely true as they were often fired after changing genders.

The job change mandate began to ease as occupations became less associated with specific genders, and with the publication of one of the earliest sets of clinical guidelines by the Harry Benjamin International Gender Dysphoria Association in 1979, which provided some consensus on psychiatric, psychological, medical, and surgical requirements for transgender people. Transgender individuals became involved with the association, which finally gave them a voice in their own medical care.

But that didn’t prompt a groundswell of transgender acceptance in the workplace. In the 1980s, a few employees successfully transitioned on the job, says Walworth, who recalls one instance at Massachusetts-based Digital Equipment Corporation, which was sold to Compaq in 1998 and later folded into Hewlett-Packard. But those positive stories were limited, in part, because it was thought that individuals who identified as transgender were extremely rare. The American Psychiatric Association’s 1994 Diagnostic and Statistical Manual of Mental Disorders, which first included “transsexualism” in 1980, found that of 30,000 people born male, one sought gender reassignment surgery; among people born female, one in 100,000 did so. “If you were a small or medium [size] company, you wouldn’t expect to have any trans people,” Walworth says. “If you had one, it was seen as a unique situation never to be repeated, so there was no need to have a policy on it.” (A 2007 study pegged the prevalence closer to one in 500.)

Caitlyn JennerFrom Vanity Fair

The push for transgender rights at work really started to gain steam after the filing of several lawsuits over related issues in the 1980s and 1990s. One of the most notable wasn’t even filed by a transgender individual; it was brought by Ann Hopkins, a manager at Price Waterhouse, who sued her employer for discrimination after being passed over for partnership when male colleagues evaluated her as too “macho.” Hopkins filed suit under Title VII of the Civil Rights Act, which bans discrimination on the basis of a person’s sex. In siding with Hopkins, the Supreme Court in 1989 prohibited employers from assuming or insisting that employees match the stereotype associated with their gender and, in doing so, effectively forbid employers from discriminating against gender-deviant LGBT employees. It was the first case to imply that Title VII’s ban on sex discrimination could cover bias on the basis of gender identity.

In another case, a transgender pilot sued Continental Airlines in the early 1990s after being terminated for undergoing gender reassignment surgery. Continental eventually settled the lawsuit and reinstated her to the cockpit. There were legislative forces at work, too: In 1993, Minnesota became the first state to protect transgender individuals from discrimination when it amended its Human Rights Act.

Those events set the stage for Mary Ann Horton, who in 1997 became a pioneer of transgender workplace rights when she lobbied her employer Lucent to add a non-discrimination policy for transgender employees. Horton wanted to cross dress openly at work at the time. Following the addition of nondiscriminatory language to Lucent’s equal opportunity policy, Horton came out at work in 1998 and fully transitioned to female a few years later.

“Once a Fortune 500 pledged not to discriminate, I thought maybe some other companies might want to do that too,” Horton told Fortune. “So I started waving the flag in the trans community, encouraging others to bring it up.”

More companies, such as Apple AAPL and American Airlines AAL , followed in the late 1990s and early 2000s before the trend picked up speed in 2002, when Human Rights Campaign introduced its Corporate Equality Index.

By 2008, the Human Rights Campaign began to push for companies to add transition-inclusive health care, and it announced that its index would require it in 2011. Transgender employees’ access to comprehensive health care was a challenge exacerbated by Medicare’s decision in 1981 to ban coverage of gender transition-related surgical procedures. (It lifted that exclusion last year.) Many private health insurance companies followed Medicare’s lead in enacting a ban, says Jamison Green, president of the World Professional Association for Transgender Health.

The addition of transgender-inclusive health care to the Human Rights Campaign’s Index helped turn that tide, as did data collected from San Francisco, which became the first major U.S. employer to publicly remove transgender exclusions from its workers’ health insurance plans in 2001. San Francisco’s data revealed that, for employers concerned about cost, transgender-inclusive health care was nothing to fear. By 2004, the city had collected $4.3 million in surcharges for the coverage, but had paid out only $156,000 on seven received and processed claims.

Ernst & Young removed transgender exclusions from its health care benefits in 2006. According to the Human Rights Campaign, some other early adopters of inclusive health care were Cisco CSCO , AT&T, and Coca-Cola KO , which began to offer such policies them around 2008 or 2009.

By that time, a few companies had also implemented transition guideline policies. Most companies adopted such guidelines out of necessity when an employee announced his or her plan to transition, says Walworth, who began consulting companies on accommodating transgender employees in 1997. Today, companies are more interested in “doing the right thing.”

Chevron CVX was a trendsetter in establishing transition guidelines in 2005. The policy defines words like gender identity, gender dysphoria, and transitioning. It provides advice for the transitioning employee—”it is important, [that] you inform key personnel who can assist you”—his or her manager, and co-workers. It addresses the bathroom issue: “Transitioning employees will be permitted to use the facilities that correspond to their gender identity. However, usage of available single-occupancy or unisex facilities may be considered for a temporary period during the employee’s transition process or on an ongoing basis.” And it encourages transitioning employees to create a workplace engagement plan that identifies the people in the company who will need to be informed about the transition and when that should happen.

Roni Lee Height notified her co-workers about her transition in January. Decades ago, the tax manager at Chevron’s offices in San Ramon, Calif. began taking female hormones. Height, who was born Ronald, had her facial hair removed about eight years ago. She wore her hair long and dyed it blonde, and she’d worn hints of makeup to work. But up until last summer, she’d wanted to stay married to her wife, so she didn’t “push the envelope too much,” she says.

Height also feared becoming destitute. She took her first job with Marathon Oil Corporation 38 years ago and has weathered the oil industry’s expansion and contraction ever since. “I’ve always been a survivor, ya know? I made it through all those companies going out of business or getting bought out and didn’t want to do anything to jeopardize my career.”

Chevron’s Roni Lee HeightCourtesy of Roni Lee Height

When Height’s wife left her last summer, she finally began to quietly speak with some of her female coworkers about transitioning. It might have stayed that way had her boss not confronted her about it. “He approached me and asked if he could help me with my issues. I thought he meant my divorce, and he said, ‘Oh no, your transition.’ It kind of floored me.”

Earlier this year, in a conference room, in front of 100 lawyers and accountants, she told her all of her coworkers about her transition at long last. “I [said], ‘Ya know, I’m still the same subject matter expert. If you have a question, please come to me.’ When I finished, the room just exploded in applause. They more than beat any expectation I had on how well this could go.”

A few steps forward, a few steps back

Transition guidelines are certainly no panacea. There’s always the risk that they will be too rigid or violate an employee’s medical privacy, says Green. “I advise corporations to only put in a written policy so that they don’t have to reinvent the wheel every time,” Green says. “They also shouldn’t make a transgender person the spokesperson for all things trans. People who are transitioning are only experts in their own story.”

Sometimes, those stories don’t go as smoothly as Chien and Height’s. Recently, there has been a rash of high-profile transgender discrimination lawsuits filed against employers. In March, Saks Fifth Avenue settled a case with a transgender sales associate who said she had been subject to harassment and retaliation because of her gender identity.

In April, a transgender former employee sued teen retailer Forever 21 for discrimination, harassment, and retaliation, claiming that a store manager in New York told her she was a “hot mess” and “disgusting.” A Forever 21 spokesperson said that the company has zero tolerance for discrimination of any sort and is taking the lawsuit “very seriously.”

In May, a transgender woman who had worked for Barnes & Noble sued the bookseller for discrimination and harassment. Barnes & Noble spokeswoman Mary Ellen Keating told Fortune that the company has a long history of supporting transgender workers. She said it works directly with transitioning employees “to provide the support they need to feel comfortable in the workplace” and with their coworkers “to ensure they are educated about the transition process and what to expect.”

Barnes & Nobel scored a perfect 100 on the Human Rights Campaign’s 2015 Corporate Equality Index. Yet, Victoria Ramirez, the plaintiff, says that as she transitioned, her manager complained about Ramirez’s appearance and told her that she was upsetting customers. The manager also emphasized that they worked in a “neighborhood store” and that Ramirez should “think of the children,” according to a complaint filed in California Superior Court in Orange County. In responding to the lawsuit in court papers, Barnes & Noble “generally [denied] each and every purported allegation and cause of action.”

As more companies adopt protections for transgender employees, the number of charges of discrimination based on gender identity filed by individual employees with the Equal Employment Opportunity Commission has increased from 161 in fiscal year 2013—the first year the agency separated gender identity bias claims from sex discrimination—to 201 in fiscal year 2014.

Kris Hayashi, executive director of the Transgender Law Center, which is representing Ramirez in her lawsuit against Barnes & Noble, says the discrimination of transgender employees “has been happening all along.” A 2011 report from The National Center for Transgender Equality and The National Gay and Lesbian Task Force found that 90% of the 6,450 transgender and gender-nonconforming people surveyed reported experiencing “harassment, mistreatment or discrimination on the job or took actions like hiding who they are to avoid it.”

Hayashi says that the big difference now is that transgender people are more aware with their rights. One case in particular was a turning point.

In 2011, Mia Macy sued the Bureau of Alcohol, Tobacco, Firearms, and Explosives after being denied a job as a ballistics forensics technician. Macy claimed she was discriminated against on the basis of gender identity and sexual stereotyping because she was rejected from the job after telling the agency about her male-to-female transition. In a historic ruling that built on the Price Waterhouse v. Hopkins Supreme Court case, the EEOC ruled in favor of Macy, finding that the ban on sex discrimination in Title VII of the Civil Rights Act included discrimination against transgender people.

Based on that ruling, the EEOC filed its first two transgender discrimination cases against private employers in September 2014. In December, the Department of Justice aligned itself with the EEOC, announcing that, going forward, it too would consider discrimination against transgender people covered by the sex discrimination prohibition in Title VII.

Those legal stances by the EEOC and DOJ are critical to strengthening workplace protections for transgender employees, but courts are not necessarily bound to them, says Marcia McCormick, an employment law professor at St. Louis University School of Law. In the meantime, 19 states and the District of Columbia have passed laws prohibiting employment discrimination based on gender identity. A proposed federal law, known as the Employment Non-Discrimination Act, that aims to ban gender identity discrimination nationwide has been introduced four times since 2007 and has never passed. All told, there’s no nationwide law that explicitly protects against gender identity discrimination (or sexual orientation discrimination, for that matter).

In that regard, corporations that have adopted anti-discrimination policies and transition guidelines are doing the same thing as companies that are paying higher minimum wages and covering the cost of college: they’re filling a void created by Congressional inaction.

“It’s been very effective at creating a sense that this kind of discrimination is wrong, probably even more so than laws,” McCormick says. “When one industry says these are the rules—especially big companies—they become best practices that people want to emulate.”

Benevolence isn’t the only motivation for companies to adopt such policies and practices; they also send a message about a company’s progressive culture, which can serve as a powerful recruiting and retention tool. “We really do want the best people for the jobs we have,” says Gary Fraundorfer, vice president of human resources at AT&T. “And the best people … come in many different forms and with different needs; there shouldn’t ever be anything that blocks us from getting the best people.”

Those fighting for transgender rights view the situation on a more basic level. Same-sex marriage, which the Supreme Court legalized last month, has been a major focus of gay and lesbian activists, but it’s the “LGB” community that’s really has owned that topic, says Horton. “Our No. 1 issue is being able to earn a living without being fired for who we are.”

Graphics by Stacy Jones