The western section extends from Moore Park in the east to Scarlett Road in the west, a distance of approximately 10 kilometres (6.2 mi).

An eastern section picks up on the far side of the Don Valley at Taylor Creek Park, extending for 7 kilometres (4.3 mi) to Kingston Road.

The eastern section of St. Clair Avenue East is serviced by the 8 Broadview and 102 Markham Road bus routes.

[1] The Grainger family, who rented a farm near the present-day intersection of Avenue Road and St. Clair, had viewed a stage production of Uncle Tom's Cabin.

Edwin added Norton to his name, and Albert chose St. Clare, although he used the incorrect spelling of St. Clair, as it was used in the theatre program.

The western end of St. Clair experienced substantial development, with the municipalities of West Toronto, Earlscourt, Dovercourt, and Oakwood established there.

This included the construction of a bridge across Nordheimer Ravine (after an earth berm collapsed)[7] as well as what was termed the Lauder Fill: the burying of the western branch of Garrison Creek, the final section to be routed into the city's stormwater system.

The construction of the Vale of Avoca through the first half of the 1920s prompted the new Toronto Transit Commission to extend the St. Clair streetcar line east to Mount Pleasant Road and then north to Eglinton Avenue.

The exception is the intersection with Yonge Street, which has experienced heavy nodal development since the opening of the St. Clair subway station there in 1954.

St. Clair Avenue was one of the few streets in Toronto wide enough to accommodate a dedicated right-of-way without significantly reducing the width of traffic lanes.

One of the largest celebrations on St. Clair Avenue was when Italy won the 1982 FIFA World Cup, which involved an estimated 300,000 fans, shutting the street down for nearly 20 blocks between Caledonia and Oakwood.

St. Clair West is also used as an umbrella term to refer to all neighbourhoods from Old Weston Road to Bathurst as they share a similar building style.

The two-day street festival attracts an estimate of 250,000–500,000 people, the majority of them being from Latinos living in Toronto and all over Ontario come together to dance, eat, shop and celebrate the culture of Latin America.