McKenna was chief development officer of Walmart U.S. until December, when she was promoted to head operations of the $288-billion-in-revenue domestic business. In her first quarter, the U.S. division’s store traffic increased for the first time since late 2012. McKenna is behind the opening of four new U.S. e-commerce fulfillment centers, the expansion of online grocery-shopping services, and Walmart’s push to open more than 200 new stores this year. She also helped lead the company’s initiative to increase starting wages to $9 in April.

For more on newcomers and returns to the list, read “Who’s on? Who’s off? Fortune’s list of the Most Powerful Women has plenty of changes.”