Thompson's two hundred acre Summer Hill estate stretched from the present day Yonge Street to Mt. Pleasant Road. On this site Thompson established the 'Summer Hill Spring Park and Pleasure Grounds'. This amusement park featured rides, games, swimming and a popular dance pavilion that was located inside the Summer Hill house. Thompson's heirs subdivided Summer Hill in the 1860's.

From the 1880's onward Summerhill's development revolved around the railway. The first residents of this neighbourhood worked at the North Toronto Railway station which was established on Yonge Street near Summerhill in the 1880's. This station - rebuilt in 1916 - is distinguished by its grand clock tower and now serves as the neighbourhood liquor store.

In the 1920's the Canadian Pacific Railway made Summerhill their main Toronto station. When Summerhill station closed this neighbourhood went into a period of decline that lasted until the Summerhill subway station opened in 1965.

The old railway station is still there and currently serves as an LCBO outlet. The station, along with the still-operational CP railway bridge, is a landmark of the neighbourhood.