Women in U.S. military service through the years

In this Jan. 31, 2005, file photo, Army Major Tammy Duckworth rolls herself up during physical therapy at the Walter Reed Army Medical Center in Washington. Duckworth lost both legs when the helicopter she was in was struck by a rocket-propelled grenade during a mission near Baghdad on Nov. 12, 2004. (AP Photo/The Arizona Republic, Michael Chow)