Geographic Regions and Area Codes

Area code 905 is part of the North American Numbering Plan (NANP) and serves the Golden Horseshoe region surrounding Lake Ontario in Southern Ontario, Canada. This area includes the Niagara Peninsula, the city of Hamilton, and the regional municipalities of Halton, Peel, York, Durham, and parts of Northumberland County, but excludes the City of Toronto. The primary area code for this region is 905, but it also has overlays with area codes 289, 365, and 742. These overlays serve the same geographic area to ensure a sufficient supply of phone numbers. The area code was established in 1993 to accommodate the growing demand for phone numbers in the region.