Antietam National Cemetery is one of the 130 cemeteries of the National Cemetery System, a system that began during the Civil War. There are 4,776 Union remains (1,836 or 38% are unknown) buried here from the Battle of Antietam, South Mountain, Monocacy, and other action in Maryland. All of the unknowns are marked with small square stones. These stones contain the grave number, and if you look closely on a few stones, a small second number represents how many unknowns are buried in that grave. There are also a few of the larger, traditional stones that mark unknown graves. In addition, more than 200 non-Civil War dead are also buried here. Veterans and their wives from the Spanish-American War, World War I and II, and Korea were also buried here until the cemetery closed in 1953.