Buried since 1887, the copper box was rumored to hold an extremely rare photograph of President Abraham Lincoln lying in his coffin. While this turned out to be false—inside, historians found Civil War artifacts, a Bible, and other historic documents—the time capsule received mounting public and media attention in the buildup to its opening.

Although the actual contents of the two time capsules discovered this month did not unearth anything new or revelatory about the era in which they were buried, their potential to hold some sort of buried secret has fascinated Americans for centuries.

The term “time capsule” can be traced back to the 1939 World’s Fair—when the Westinghouse Electric & Manufacturing Co. buried a box of common household items in Flushing Meadows, New York. The capstone of the capsule is still on display at the burial site, and is not meant to be opened again until the year 6939. 

The concept of burying commemorative objects underground to be preserved and opened years later, however, was not invented with the term in 1939, and over the past few decades, there have been several other time capsules that have been uncovered in America, garnering national media attention.

Here are a few of the biggest time capsule discoveries in recent history:

18TH-CENTURY MASSACHUSETTS STATE HOUSE TIME CAPSULE

In 2014, a box was found outside the Massachusetts state house that had been buried by Paul Revere and then–Massachusetts Gov. Samuel Adams more than two centuries earlier.

Believed to be the oldest time capsule ever discovered in the United States, it took over an hour for historians to carefully remove all of the small box’s contents in early 2015. 

“It was like brain surgery, with history looking down on us,” Malcolm Rogers, director of Boston’s Museum of Fine Arts, said at the time. 

Inside, historians found five folded newspapers, a Massachusetts commonwealth seal, a title page from Massachusetts colony records, and at least 24 coins and a silver plate likely made and inscribed by Revere.

OLD STATE HOUSE LION’S HEAD CAPSULE

In October 2014, a classic golden statue of a Lion outside Boston’s Old State House was taken down for restoration. Inside the lion’s head, historians found a time capsule that had been placed there by the lion’s sculptor in 1901, over a century earlier.

The next week, an archivist contracted by the Bostonian Society carefully opened and examined the contents of the small box. 

Inside, archivists found dozens of items from the time, including various newspapers from Boston in 1901, campaign buttons for various politicians including President Teddy Roosevelt, photographs of several late-1800s Boston mayors, and wood removed from the previous statue of a lion that was replaced by the restored, golden lion.

After the statue was restored, a new time capsule was placed inside the lion’s head to be discovered the next time it is due for restoration. 

1876 CENTURY SAFE

While the two aforementioned time capsules were buried, forgotten about, then rediscovered years later, the 1876 Century Safe was the world’s first planned time capsule.

To mark the country’s 100th anniversary, New York magazine publisher Anna Deihm buried an iron box stuffed with relics from the 19th century during a ceremony in Philadelphia. 

One hundred years later in 1976, when the country was celebrating its bicentennial, the box was opened in a ceremony attended by then-President Gerald Ford. Inside, the time capsule contained a gold pen, a book on temperance, and photographer Matthew Brady’s images of President Ulysses S. Grant and other politicians of the era, among other artifacts. 

DETROIT CENTURY BOX

Much like the time capsule buried in Philadelphia in 1876, this copper time capsule was hidden away in 1900 by then–Detroit Mayor William C. Maybury with instructions for it to be left alone until the year 2000.

The time capsule was opened at the turn of the 21st century by Detroit Mayor Dennis Archer in December 2000. 

Inside, archivists found dozens of letters written by the city’s business and political leaders describing life in Detroit in 1900 and making predictions about what life would be like a century later. 

“We travel by railroad and with steam power from Detroit to Chicago in less than eight hours and to New York City by several routes, in less than 20 hours. How much faster are you traveling?” asked Mayor Maybury in his letter.