The National Archives has records of numerous freedom suits filed in the District of Columbia’s federal court. This petition was written on behalf of a free man who had been jailed as a runaway. Slaves were emancipated in the nation’s capital in April 1862, about one year before the Emancipation Proclamation of January 1863.
“Mr. Sam Snowden will prove him to be free” 1821
National Archives, Records of the District Courts of the United States