They were domestics and carpenters and metal workers, husbands and wives and children–about 3,200 people enslaved in the nation's capital when the Civil War broke out. On April 16, 1862, eight and a half months before the Emancipation Proclamation, they were freed by Congress through the D.C. Compensated Emancipation Act.It was the first time the federal government set slaves at liberty. Now rare details of those lives are emerging, as scholars transcribe and study the petitions filed by slave owners seeking compensation under the 1862 law. "It's the largest set of information about any one group of slaves in American history that I know of," says Kenneth J. Winkle, a professor of American history at the University of Nebraska at Lincoln. "People, including me, will be working with this information for years."[Personal note: As I will obnoxiously remind people from time to time, I grew up in DC, so I'm especially glad to have gotten a chance to do this story.]