St Marys is in southwestern Ontario, Canada. It is located on the Thames River southwest of Stratford in Perth County, and surrounded by the Township of Perth South.
In 1841-43 Thomas Ingersoll, a brother of Laura Secord, erected a sawmill and a grist-mill and in return obtained 337 acres of land in the vicinity from the Canada Company. The mills formed the nucleus of the settlement which in 1854 was incorporated as the village of St Marys. The building of railways, 1857-60, simulated development and in 1864, when St Marys became a town, it was already the centre for lumber and limestone quarry industries and the adjacent prosporous agricultural region.
The town is known as "The Stone Town", due to the abundance of limestone in the surrounding area, giving rise to a large number of limestone buildings and homes throughout the town. St. Marys Cement, a large cement producer founded in the town, capitalized on this close feedstock, and grew to be a major producer of cement in the province of Ontario.
Canada's 9th Prime Minister, Arthur Meighen was born in Anderson just west of St Marys. His family moved to St Marys and Meighen atttended the St Marys Collegiate Institute. He is buried in St Marys Cemetery.
The Canadian Baseball Hall of Fame moved to St. Marys from Toronto in 1994 and opened in 1998. It is dedicated to preserving Canada's baseball heritage.
The town's junior hockey team, the St Marys Lincolns, play in the Greater Ontario Junior Hockey League.