 In late 1863, the fort was renamed after Major General John F. Reynolds, who was killed on 1 July at the Battle of Gettysburg in Pennsylvania.Before the outbreak of the Civil War, Alexandria County (renamed Arlington County in 1920), the northernmost county in Virginia and the closest to Washington, D.C., was a predominantly rural area.Originally part of the District of Columbia, the land now comprising the county was retroceded to Virginia in a July 9, 1846 act of Congress that took effect in 1847.