Located near Washington, D.C., Fairfax County was an important region in the Civil War. The Battle of Chantilly or Ox Hill, during the same campaign as the second Battle of Bull Run, was fought within the county; Bull Run is the border between Fairfax and Prince William Counties. Other areas of activity included Minor's Hill, Munson's Hill, and Upton's Hill, on the county's eastern border, overlooking Washington, D.C.