African Americans at the Siege of Petersburg African Americans at the Siege of Petersburg . In Petersburg . At the beginning of the American Civil War , Virginia had a black population of about 549 , 000 . This meant that of the Confederacy ' s total black population one in six blacks lived in Virginia . Of those African Americans in Virginia 89 % were slaves . In Petersburg about half the population was black of which nearly 35 % were free . Petersburg was considered to have the largest number of free blacks of any Southern city at that time . Many of the freedmen prospered here as barber s , blacksmiths , boatmen , draymen , livery stable keepers , and caterers . Serving the Confederacy . When Petersburg became a major supply center for the newly formed Confederacy and its nearby capital in Richmond , both freedmen and slaves were employed in various war functions . One of which was working for the numerous railroad companies that operated in and out of the city . In 1862 Captain Charles Dimmock used freedmen and slave labor to construct a ten - mile long defensive line of trenches and batteries around the city . Once the siege began in June 1864 , African Americans continued working for the Confederacy . In September 1864 , General Robert E . Lee asked for an additional 2 , 000 blacks to be added to his labor force . On January 11 , 1865 General Robert E . Lee wrote the Confederate Congress urging them to pass pending legislation to arm and enlist black slaves in exchange for their freedom . On March 13 , the Confederate Congress passed legislation to raise and enlist companies of black soldiers . The legislation was then promulgated into military policy by Davis in General Order No . 14 on March 23 , 1865 . The emancipation offered , however , was still reliant upon one ' s master agreement ; " no slave will be accepted as a recruit unless with his own consent and with the approbation of his master by a written instrument conferring , as far as he may , the rights of a freedman " Serving the Union : U . S . Colored Troops in the Siege . During the war a total of nearly 187 , 000 African Americans served in the Union Army . Of those the greatest concentration of U . S . Colored Troops ( USCT ) was at Petersburg . In the initial assault upon the city on June 15 , 1864 a division of USCTs in the XVIII Corps helped capture and secure a section of the Dimmock Line . The other division at Petersburg was with the IX Corps and it fought in the Battle of the Crater , July 30 , 1864 . In December 1864 , all the United States Colored Troops around Petersburg were incorporated into three divisions and became the XXV Corps of the Army of the James . It was the largest black force assembled during the war and varied between 9 , 000 to 16 , 000 men . Overall in the Petersburg Campaign USCTs would participate in 6 major engagements and earn 15 of the 16 total Medals of Honor awarded African American soldiers in the Civil War . At City Point . African Americans served in varying capacities at the Union supply base at City Point . They served as pickets , railroad workers , and laborers " discharging the ships , wheeling the dirt , sawing the timber and driving the piles . " Many also worked at the Depot Field Hospital as cooks .