The Town was hewn from almost unbroken virgin forests which had been home to the Huron Indians, and was first surveyed in 1820.

The area encompassed 68,653 acres (278 km2), including the villages of Allandale, Tollendal, Painswick, Minets Point, and Holly at the time.

During this period, post offices, churches, and stores were established, also a form of local government performed by commissioners was appointed under a provincial act.

The first school was built in 1838 and located at Myers Corners, later called Victoria (now the community of Stroud).

The continued building of public roads, together with the railway and the lake navigation, resulted in the establishment of more flourishing hamlet settlements.

However, paved roads, the automobile (the first recorded in the town was 1912), the price of fuel, and the cost of housing outside Toronto, encouraged commuter residents.

In 1967, 597 acres (2.4 km2) were annexed from Innisfil by the City of Barrie to accommodate the establishment of the Formosa Spring Brewery.

The modern brewery was located on the northwest corner of the land, beside Ontario Highway 400, a notable landmark due to its three large and brightly coloured tanks.

Molson then sub-let the brewery buildings to other businesses while selling off the land, before the it closed entirely and forms today's Park Place.

The County of Simcoe Act provided for further restructuring of Simcoe County on January 1, 1994, when the Village of Thornton was amalgamated with the Township of Essa and a small section of the Township of Essa, adjacent to Cookstown, was amalgamated with Innisfil.

The province of Ontario enacted legislation that enabled the City of Barrie to annex 2,293 acres (9.28 km2) from the Town of Innisfil on January 1, 2010.

[6] In 2019, Cortel Group proposed a long-term transit-oriented development, dubbed The Orbit, around the station with the goal of 30,000 people living in the area in the near future.

That November, Innisfil Town Council approved The Orbit as Cortel committed to funding the station.

The town is part of the provincial riding of Barrie—Innisfil, represented by Andrea Khanjin of the Progressive Conservative Party of Ontario, and part of the federal riding of Barrie—Innisfil, which was introduced for the 2015 federal election, and represented by John Brassard of the Conservative Party of Canada.

The Barrie line of the GO Transit commuter rail system passes through Innisfil, but does not stop in the town, [17] although a planned future station is awaiting construction.

[19] The service began in 2017 and attracted 8,000 monthly trips in its first year, but fares were increased in 2019 due to the rising cost of the subsidy.

Cookstown is also known for its annual garage sale called "Wing-Ding" which occurs the first weekend of June every year.

Georgian Downs Harness racetrack and casino is located on the 5th Sideroad near the Highway 400 interchange at Innisfil Beach Road.

The Sunset Speedway, located on Yonge St. south of Innisfil Beach Road, has been a local landmark for over 50 years.