lexandria may be said to be a finished city
. . . it bears all the marks of decay," wrote one visitor in 1852. But retrocession brought about a period of prosperity lasting until the Civil War. New railroads beginning in 1851, active banks, new industry, and a booming slave trade, contributed to prosperity. The population grew from 8,700 in 1850 to 12,650 in 1860. Quality of life improved, too, as a gas light company began in 1851 and a new water system was installed in 1852.

The issue of slavery, however, would not go away. Growing sectional tensions climaxed with John Brown's raid on Harpers Ferry in 1859, Lincoln's election, secession in the Deep South, and fighting at Fort Sumter. On May 23, 1861, Alexandrians approved secession by 958 to 106. As Union troops prepared to occupy the city, hundreds of Alexandrians, led by former resident Robert E. Lee, left to fight for the Confederacy.

On May 24, 1861, Union forces occupied Alexandria. Colonel Elmer Ellsworth and hotelkeeper James Jackson became martyrs for the Union and Confederacy respectively in a fight over the Confederate flag.