It passes through the communities of Gray's Beach, Halsteads Bay, Ivy Lea, Darlingside, Rockport, Narrows, La Rue Mills and Mallorytown Landing, as well as providing access to the three inland properties of the Thousand Islands National Park.

Evidence of its former use can be seen today in the wide right-of-way; the unused westbound lanes now serve as a recreational trail and twin bridges span two locations along the parkway.

The Thousand Islands Parkway is a scenic route along the St. Lawrence River between Gananoque and Brockville through the rugged terrain of the Frontenac Arch, a protrusion of the Canadian Shield southward into New York state.

However, because of the residential properties and the scenic nature of the parkway, a new inland route known as the Thousand Islands Bypass was constructed for Highway 401 through the mid-1960s.

It meets Highway 137 at an interchange at the parkways midpoint; the Ontario approach to the Thousand Islands Bridge which continues as Interstate 81 south of the Canada–United States border.

The parkway continues northeast, serving the riverside communities of Darlingside, Rockport, Narrows, La Rue Mills and Mallorytown Landing.

[6] By 1935, with early construction underway on the Thousand Islands Bridge,[7] Fulford had convinced the incoming Minister of Public Works and Highways, Thomas McQuesten, of the merits of a scenic route for tourism and as a depression relief project.

[6] McQuesten, who was seeking to build a trans-provincial divided highway, decided the river road would be the ideal route through the rough terrain between Gananoque and Brockville.

[8] On April 29, 1937, The Ontario Department of Highways (DHO), predecessor to the modern Ministry of Transportation, formally announced the building of the St. Lawrence River Road.

[12] In preparation, the 13.8 km (8.6 mi) portion of the parkway west of Ivy Lea was quickly gravelled to provide access to the new bridge.

[6] A section between Mallorytown Landing and Butternut Bay was opened in October 1938 as a two-lane gravel road with a temporary bridge crossing Jones Creek.

James Auld, MPP for Leeds and the Minister of Tourism and Information, joined local residents to persuade the DHO to construct an inland bypass.

[37] Despite the expected influx of traffic from the United States for Expo 67 in Montreal, the DHO opted to build the portion east of Ivy Lea after the centennial celebrations.