Eglinton Avenue is a major east–west arterial thoroughfare in Toronto and Mississauga in the Canadian province of Ontario. The street begins at Highway 407 (but does not interchange with the tollway) at the western limits of Mississauga, as a continuation of Lower Baseline in Milton. It traverses the midsection of both cities and ends at Kingston Road. Eglinton Avenue is the only street to cross all six former boroughs of Metropolitan Toronto. The Toronto section was surveyed in the 19th century as the Fourth Concession Road (with the first being Queen Street). It was historically known as Richview Sideroad in Etobicoke and Lower Baseline in Mississauga. It was also designated Highway 5A (and later Highway 109) in Scarborough. History There are two sources for the naming of Eglinton Avenue. Henry Scadding in an early history of the city wrote that it originated from Eglinton Castle in Scotland, itself named for the Earls of Eglinton. Several early settlers, impressed by the Eglinton Tournament of 1839 hosted by the 13th Earl, named the hamlet developing in the area as the Village of Eglinton after the Earl. More likely is the humbler story that it was named by the tavern keeper John Montgomery who settled in the area in 1830 and named the village after the Earl of Eglinton of the Montgomerie family, to whom he believed he had a family connection. The wagon trail connecting to Yonge between the third and fifth concessions (St. Clair and Lawrence Avenues respectively) soon adopted the name of the village and was gradually improved over the years near Yonge Street. In 1890, the area was incorporated as North Toronto, and in 1912, it was annexed to Toronto itself. In 1953, Metropolitan Toronto (commonly known as Metro) was formed. Seeking to build new connections to the rapidly developing suburbs, Metro widened and interconnected Eglinton to its current form through the decade. The eastern segment through Scarborough was known as Highway 5A between 1937 and 1953; this number also appeared on St. Clair Avenue West until 1952 when the Toronto Bypass, (the precursor to Highway 401), opened between Weston and Highway 11 (Yonge Street). The two pieces of "Highway 5A" were never connected. In 1953, what remained was renumbered as Highway 109; a year later, the road was removed from the provincial highway system. Because of its time as a provincial highway, the road through Scarborough was widened