Thornhill, Markham and Vaughan, Markham

Thornhill, on Both Sides of Yonge

Thornhill has two addresses and one history. Yonge Street splits it between Markham on the east and Vaughan on the west, so a town-wide search for it can come up short. This page sits with Markham because the heritage plan and Heintzman House are on that side, but Thornhill's village life crosses the road and the Vaughan side counts too.

Last reviewed November 1, 2026 by the York Happening editorial team.

Heintzman House

Anthony Hollingshead, a Loyalist, built a two-room house on Yonge Street land by 1802. George Crookshank bought the farm, called Sunnyside, in 1817, and City sources differ on when the larger brick house went up. Charles Theodore Heintzman bought the property in 1930.

After the family's time, residents pushed to save it, and the Town of Markham bought it in 1966. The City now rents it for weddings and events, and tours are by appointment. The 2026 Artisan Craft Show runs on November 14 and 15, from 10 a.m. to 5 p.m.

Heintzman House

City-owned heritage house and event hall.

135 Bay Thorn Drive, Thornhill, Markham

Source

Village stops

Markham keeps a heritage conservation district plan for its side of the old village. Two library branches serve the Markham side. Thornhill Village Library is on Colborne Street and closes on Mondays. Thornhill Community Centre Library is on Bayview Avenue and opens seven days a week.

Thornhill Village Library

A branch in the old village.

10 Colborne Street, Markham

Source

Thornhill Community Centre Library

A branch on the east side.

7755 Bayview Avenue, Markham

Source

The Vaughan side

West of Yonge, the same community falls under the City of Vaughan, and its parks, pools and programs appear on Vaughan's lists. Search both city sites when you look for a Thornhill pool or a skate. See the Vaughan guide for the rest of that city.

Thornhill Community Centre Library · 6:00 PM - 7:30 PM

Free

Frequently Asked Questions

Is Thornhill in Markham or Vaughan?

Both. Yonge Street divides it, with Markham to the east and Vaughan to the west.

What is Heintzman House?

A City of Markham heritage house in Thornhill, now used as a meeting hall and event space.

Who bought Heintzman House in 1966?

The Town of Markham bought it after local residents worked to save it.

Sources

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