Area code 289 is an overlay for southern Ontario, Canada, covering the same region as area code 905, including cities like Hamilton, Mississauga, Niagara Falls, and Oshawa. Introduced in 2001 due to rapid population and telecom growth in the Greater Toronto Area (GTA), it was followed by another overlay, 365, making ten-digit dialing mandatory. The 289 area supports a bustling region known for industry, tourism, and suburban expansion. It plays a crucial role in facilitating communication in one of Canada’s most dynamic and densely populated corridors.