John Killian memorial in section B of Prospect Hill Cemetery in Washington, D.C., in the United States in 2014. Prospect Hill Cemetery was added to the Register of Historic Places of the District of Columbia (a listing of historic sites maintained by the city) in 2005. Killian was a board member of Prospect Hill Cemetery, Inc., in 1867. His limestone memorial is one of the more ornate memorials in the cemetery. Both granite and limestone were used in cemeteries in the mid-Atlantic region of the United States in the 1800s. This was unusual both at the time and today, as limestone is a soft rock and easily weathers away.