The 31.1-kilometre-long (19.3 mi) route began and ended at Highway 18, travelling along the Lake Erie shoreline and through Colchester.

Highway 18A was a short route that served the headland that protrudes into Lake Erie between Amherstburg and Kingsville in the southernmost part of Essex County.

The route itself was 31.1 kilometres (19.3 mi) long, detouring to the south along the shore of Lake Erie and passing through Colchester.

Essex County council requested that the lakefront road between Malden Centre and Kingsville be taken over by the province and designated Highway 18A in June 1935.

[8][9] Following recommendations presented in the Selkirk Report in June 1976, the renamed Ministry of Transportation and Communications rebuilt the road to proper standards, including bypassing several corners; the bypassed route is now Twin Gables Drive and Dolson Road.