Many slaves saw the arrival of the Union army in Stafford, opposite Fredericksburg, in April 1862 as a chance for freedom. Over the next few months, slaves from Fredericksburg, Stafford, Spotsylvania and other surrounding counties fled to the Union army. It was likely the largest single exodus [mass departure] of slaves in America up to that time.
However, the crossing of the Rappahannock was not the end of their journey, but the beginning. African Americans worked to gain true freedom for the next 100 years.