East York was originally part of York Township, Ontario. Following the incorporation of the Township of North York in 1922, York Township was divided by Toronto, Leaside and North Toronto.
With the rapid growth that followed the opening of the Bloor-Danforth (Prince Edward) Viaduct in 1918, the residents of the eastern half of York Township (as an exclave of the western half) felt they had been neglected by the township when it came to roads, sewers and other municipal services.
Left with the option to either join the City of Toronto or branch out on its own, 448 East Yorkers voted to incorporate a new township, while 102 voted to amalgamate with Toronto.
The Township of East York was incorporated on January 1, 1924 with a population of 19,849. The western half of York Township retained its name.