In the American Civil War as you all know Virginia succeed from the Union and Washington D.C. was in Virginia (I know that it was it's own District). So of there were units from the Union like 150th Pennsylvania and Confederates had units like the 17th Virginia (Just random units). So what did they call the troops from D.C.? Did they call them a Virginia units or maybe Maryland (because it is near by) or did they call something else? (I am just wondering because I don't see any units like the 3rd D.C. or anything like that)
Two regiments of infantry (the 1st and 2nd District of Columbia Infantry Regiments), four battalions of infantry (the 2nd, 3rd, 5th, and 8th District of Columbia Infantry Battalions), and one regiment of cavalry (the 1st District of Columbia Cavalry Regiment) were raised for the Union by the District of Columbia. The 1st District of Columbia Infantry was organized in the summer of 1861, while the 2nd District of Columbia Infantry was mustered into service in February 1862. The 1st District of Columbia Cavalry formed four companies from June to December 1863, and eight cavalry companies from Maine were later attached to the regiment, seven of which were later detached and assigned to the 1st Maine Cavalry.
Thirty-three named companies of infantry and one named company of cavalry were raised from the Washington militia for local defense, serving from April to July 1861 in Washington proper. The infantry battalions also served from April to July 1861.
The only units to see significant action outside of the borders of Washington were the infantry and cavalry regiments, although the infantry battalions did move to Montgomery County, Maryland, during the summer of 1861 before their muster out of service. the 1st District of Columbia Infantry was assigned to the 2nd Division, II Corps, Army of Virginia, and fought at the Battle of Cedar Mountain in August 1862 and was in reserve during the Second Battle of Bull Run in August 1862. It was reassigned to the defenses of Washington following the battle and was mustered out of service on 12 September 1865. The 2nd District of Columbia Infantry was assigned to the 1st Division, V Corps, Army of the Potomac, and was in reserve during the Battle of Antietam (September 1862) and the Battle of Fort Stevens (July 1864) before returning to the defenses of Washington; it was consolidated with the 1st District of Columbia Infantry on 28 February 1865. The 1st District of Columbia Cavalry served in the Siege of Petersburg, and later the Appomattox Campaign in the spring of 1865. The regiment served in Virginia for the remainder of the war until being mustered out of service on 26 October 1865.
Sources:
Dyer, Frederick H. A Compendium of the War of the Rebellion. New York: Thomas Yoseloff, 1959.