Johnstown, County Kildare derives its name from a now-ruined church dedicated to St John and believed to have been built in late-Medieval period by the Knights Hospitallers (now otherwise known as the Knights of Malta). The centre of the building is now dominated by a large High Cross commemorating Richard Bourke, sixth Earl of Mayo who was assassinated in 1872 while serving as Viceroy of India; his home was at nearby Palmerstown. An earlier owner of this property was the Flatesbury family, and set into the north wall of the church is a grave slab featuring their coat of arms and those of the Wogans, below an eight-armed cross. This carries the date 1289 although the slab is thought to date from the 15th century.