It is immediately south of Richmond Hill.
Thornhill was founded in 1794. Its first settlers on Yonge Street in Thornhill were Asa Johnson (who settled on the Vaughan side) and Nicholas Miller (who settled on the Markham side). Of particular importance was the arrival of Benjamin Thorne in 1820, who was operating a gristmill, a sawmill, and a tannery in the community. The settlement came to be known as Thorne’s Mills, and later, Thorne’s Hill, from which its current name is derived. (Thorne committed suicide in 1848, after a serious wheat market crash.)
Between 1830 and 1848, Thornhill experienced a period of continued growth and prosperity. The business district of Thornhill developed on its portion of Yonge Street, between Centre Street and John Street. Stagecoaches travelled between Holland Landing (Lake Simcoe) and York (Toronto) as Yonge Street’s road conditions improved with new stonework. During this prosperous period, several churches, many of which are still standing today, were constructed.
Thornhill’s location along Yonge Street, a major transportation route, proved to be beneficial to the community’s growth throughout much of the twentieth century. The implementation of an electric street railway along Yonge Street in 1898 towards Kleinburg, Georgina, King and Toronto meant that, for the first time, it was possible for people to reside in Thornhill and work in Toronto. By the 1920s, the prevalence of the automobile further facilitated travel along Yonge Street.
In 1931, Thornhill became a “Police Village“; before that time, Thornhill had no independent status and was split between the townships of Vaughan and Markham along Yonge Street, since the creation of municipal government in 1850. Before 1931, each township administered its own half of the village. The creation of the Police Village gave Thornhill its own political boundaries. The village was headed by a reeve.
In 1971, York Region was created, part of a wave of municipal re-organization which converted many townships into towns and eliminated many of the municipal forms of organization which had existed within those townships. The establishment of a regional administration effectively eliminated the Police Village of Thornhill. Thornhill’s administration reverted to the newly formed towns of Markham and Vaughan at this time.
However, many political and social institutions remained organized around the former municipal entities eliminated in 1971. Like neighbouring communities such as Woodbridge, Maple, and Unionville – as is typical for most urbanized former Greater Toronto Area (GTA) villages outside of the City of Toronto – Thornhill remained the postal designation for addresses within the former village’s boundaries, and community organizations such as local newspapers, sports teams, and schools continued to operate under the Thornhill name and designation. As an example, until the mid-1990s residents of Thornhill seeking to play high-level hockey were required to play for a Thornhill team.
While the old village of Thornhill revolved around Yonge Street between Centre and John Streets, the community is typically thought to be located between Dufferin Street to the west, Highway 7 to the north, Steeles Avenue to the south, and Highway 404 to the east.
A minor February 2008 snowstorm in Thornhill.
Thornhill’s growth since the 1960s and 1970s has been largely connected to its location bordering what is now the City of Toronto. Large housing developments, particularly beginning in the 1980s with such projects as the Tannenbaum family’s Spring Farm area near Bathurst and Clark.