St. Lawrence Hall was built by the City of Toronto in 1850. Designed by architect William Thomas in the Italianate style, it provided an elegant meeting place for Toronto's 19th-century elite. The ground floor was designed as commercial space, the second as offices, and the third to house a 1000-seat assembly room. The building was a major cultural venue for lectures, concerts, balls and receptions attended by the city's most notable citizens. These events included several important Abolition meetings in the years when Canada was receiving thousands of Underground Railroad refugees from American slavery. St. Lawrence Hall was restored in 1967, and has once again become an active cultural centre.

St. Lawrence Hall was designated a national historic site in 1967 because:
- designed in the renaissance tradition, this hall was for many years Toronto's chief social and cultural centre;
- it ranks amongst the finest of 19th-century Canadian public buildings; and
- it was a place of gatherings of the Abolitionist movement.