Provincial highways in Nova Scotia
Trunk 4 is part of the Canadian province of Nova Scotia's system of Trunk Highways. The route runs from Highway 104 exit 7 at Thomson Station to Glace Bay. Until the construction of the Trans-Canada Highway, Trunk 4 was a major traffic link in northern Nova Scotia and Cape Breton, and is still used on Cape Breton as an alternative to Highway 105.
The highway was originally called the King's Highway, however, this name is no longer applied to the entire road. The only remaining historic section of the highway that maintains the name "King" is King's Road in Sydney.
The section between the western terminus at Exit 7, Highway 104 in Thomson Station to Mahoneys Corner was originally built as Highway 104 in the 1960s. It was bypassed by the Cobequid Pass in 1997 and redesignated Trunk 4 at that time.
The section between Mahoneys Corner and Glenholme was originally part of Trunk 4 until the 1960s when it was designated Highway 104. This section was also redesignated Trunk 4 in 1997 after the opening of the Cobequid Pass.