The abbreviation “U.S.C.T.” on a tombstone stands for “United States Colored Troops”. U.S.C.T. Regiments were composed of African-Americans, many former slaves, who volunteered for service in the Union Army during the Civil War.

The National Park Service has a detailed history of the U.S.C.T. at this web site.

Other web sites focusing on the USCT include the US Colored Troops Institute for Local History and Family Research.