Mount Dennis is named after John Dennis, a Loyalist shipbuilder from Philadelphia who settled on a farm in the early 1800's.

The Dennis family managed a saw mill and a woolen factory on their property. In the late 1800's, Mount Dennis was recognized for its brick yards, the Conn Smythe Sand and Gravel pit, and a few market gardens on the productive field of what is now Eglinton Flats.

In 1893 Mount Dennis completed its first school which was then followed by a post office and some general stores along Weston Road.
In 1916 the Kodak Company displaced into Mount Dennis and became the areas largest employer.

By the 1920's, Mount Dennis had developed to the point where a poll was held concerning its incorporation as a Town. The "No" vote won and Mount Dennis continued to be part of what was then York Township.

During the 1950's the huge open terrains and bush in this area gave way to new subdivisions as Mount Dennis advanced from a rural settlement to an urban neighborhood.