Former counties of Ontario
The Canadian province of Ontario has several historic counties, which are past census divisions that no longer exist today. Most historic counties either merged with other counties, or became regional municipalities or single-tier municipalities. Although counties had existed prior to 1849, after 1849 they replaced the district systems in administering local government and courts in Ontario. The county system is used in southern, southwestern and eastern sections of the province of Ontario. There are no counties in Northern Ontario due to sparse population and a long-standing boundary dispute with the Northwest Territories (that was not resolved until 1912). Counties Addington County (1792–1864) merged with Lennox County to form Lennox and Addington County Brant County (established 1852) split into the single-tier 'county' of Brant and the city of Brantford Carleton County (1800–1969) became the Regional Municipality of Ottawa-Carleton, now the City of Ottawa, a single-tier municipality. Dufferin County (established 1881) created from parts of Simcoe, Grey and Waterloo counties. Durham County (1792–1973) portions merged with Ontario County to form Durham Regional Municipality. Remaining portions joined Northumberland, Peterborough and Victoria Counties. Grenville County (1792–1850) merged with Leeds County to form Leeds and Grenville United Counties Kent County (1792–1998) became the single-tier Municipality