Highway4 was originally designated in 1920 when the provincial government assumed the road running from Talbotville Royal (St. Thomas) to the Northern Highway (later Highway7) at Elginfield, via London. The portions within Elgin County were assumed on August4, while the portions south of London were assumed on June24. The portions north of and through London were assumed on August6. The route featured a concurrency with the Provincial Highway (later Highway2) between Lambeth and downtown London. Until the summer of 1925, Ontario highways were named rather than numbered. When route numbering was introduced, the route between St. Thomas and Elginfield became Provincial Highway4. 1927 saw several new sections of road assumed that would become portion of Highway4. On September14, the route was extended to
Highway 8 at Clinton. Further north, a new highway was created on June22, 1927, between
Highway 9 at
Walkerton and
Highway 6 at
Durham. This latter section was designated as Highway4A. On March12, 1930, Highway4 was extended to Durham, fully absorbing the route of Highway4A in the process. Two months later, on May11, it was extended south to Bedford Street (now Edith Cavell Boulevard) in Port Stanley. On April11, 1934, the highway was extended east to the intersection of
Highway 10 in Flesherton. Highway4 reached its maximum length of when it was extended from Flesherton to
Highway 24 in Singhampton in the mid-1970s.
Downloads from the
Highway 402 interchange in
London As part of a series of budget cuts initiated by premier
Mike Harris under his
Common Sense Revolution platform in 1995, numerous highways deemed to no longer be of significance to the provincial network were decommissioned and responsibility for the routes transferred to a lower level of government, a process referred to as downloading. Portions of Highway4 were transferred to the counties of
Elgin,
Huron,
Bruce and
Grey on January1, 1998. The former portion of Highway 4 south of St. Thomas is now signed as
Elgin County Road 4. The former northern portion is broken into several different roads: •
Huron County Road 4 from
Clinton to near
Wingham •
Bruce County Road 4 (London Road) from near Wingham to Riversdale • A former
concurrency with Highway9 between Riversdale and Walkerton •
Grey County Road 4 from Walkerton to
Simcoe County Road 124 just south of Singhampton In 2017, the
City of London announced that Highway 4 through London would be re-signed and re-routed via Richmond Street, Sunningdale Road, and Wonderland Road, resulting in a short
concurrency with Highway 401 between the Colonel Talbot Road and Wonderland Road interchanges. ==Major intersections==