During the Civil War, Confederate and Union troops surged back and forth through Centreville. For a time the church served as a battlefield hospital. In 1862, St. John's was used as a Confederate encampment. Most of the trees surrounding the church were destroyed by the 40,000 Confederate troops who wintered there, in order to build fires and erect hutments. The ravages of war nearly ruined Centreville due to its strategic location and many graves and monuments on site tell the story of what happened during this poignant time in American history.