For a brief description of Camp Stanton, see letter, William Henry Johnson to his parents, 11 February 1862.
appearance They started provost duty the week after 11 February 1862, and 'each man is to be furnished with two pairs of white gloves[,] and any man found drunk with his cloth[e]s dirty will be put in the guard house' (letter, William Henry Johnson to his parents, 11 February 1862).
overall duty According to Andrew Brown (C), they were guarding the railroad station, the prison (perhaps the Old Capital Prison?), the Long Bridge, the Chain Bridge, and the Barracks. (letter, Andrew Brown to his father and sister, 29 March 1862, Washington DC)
According to Brown, in April 1862, they had guard duty every fourth day (letter, Andrew Brown to his father and sister, 17 April 1862, Carroll Hill Barracks Washington DC). In August, however, they had guard duty every third day, in Alexandria (letter, Andrew Brown to his father and sister, 4 August 1862).
Bridges The 91st was responsible for guarding bridges, including the Long Bridge.
Central Guard House The Central Guard House was originally intended to hold soldiers temporarily. Its use expanded as the need for prisons outstripped their availability.
Old Capitol Prison The Old Capitol Prison had been the US Capitol, and then a boardinghouse. During the Civil War, it held Union soldiers, and also political prisoners, including Rose O'Neal Greenhow.
Douglas Hospital They had sentinels at Douglas Hospital, Washington DC (and on 14 April 1862, Patrick Gallagher and Joseph Keen were arrested for being drunk on duty as sentinels there)