History of Provincial Highway 4A:
Provincial Highway 4A was a temporary designation applied to a discontinuous section of Highway 4 in the Walkerton area in the 1920s while the rest of Highway 4 between Clinton and Walkerton was being upgraded. Highway 4A passed through Bruce and Grey Counties. The route ran from the Highway 9 Junction in Walkerton to the Highway 6 Junction in Durham. In May 1927, Preliminary Route Plans were drawn up showing the proposed assumption of the Durham Road between Walkerton and Durham. The 29 km road between Walkerton and Durham was first assumed by the Department of Public Highways of Ontario (DPHO) on June 22, 1927. Sections of the new highway within Walkerton, Hanover and Durham were not assumed by the DPHO, so those sections of the route remained under municipal jurisdiction. The entire route of Highway 4A was gravel-surfaced. The Highway 4A designation proved to be very short-lived. Once Highway 4 had been completed and assumed between Clinton and Highway 9 west of Walkerton in 1930, it opened up a continuous through highway from Clinton to Durham. The temporary Highway 4A designation was therefore no longer needed. In 1930, the DPHO took the opportunity to renumber Highway 4A as part of the new Highway 4 extension.
The Highway 4A designation was permanently retired and was never used again in Ontario. Provincial Highway 4A was one of only two highways in Ontario that came into existence and disappeared prior to the changeover to the King's Highway designation in 1930. The other route was the Port Hope to Peterborough Highway (Highway 12A) which was renumbered as Highway 28 in 1928. Thus, Highway 4A and Highway 12A are the only highways in Ontario that were known solely as a "Provincial Highway" since they were not in existence when the "King's Highway" designations were first assigned in 1930.