The Mid-Peninsula Highway has been part of Ontario Ministry of Transportation planning since as far back as the 1950s, but was resurrected in the early 1990s to relieve traffic congestion along the Queen Elizabeth Way, which runs through tender fruitlands and is not well-suited to expansion beyond its current configuration. The governments of Premier Mike Harris and Ernie Eves planned to fast-track the highway's construction, but the project has been delayed by the Dalton McGuinty government through re-initiating the environmental assessment that was completed by the previous governments. Plans have also been stalled due to the reluctance of private owners to sell the land needed for the freeway.
The QEW-Highway 420 interchange has been once considered as the eastern terminus of the route (which could see the Mid-Peninsula bypass being signed as Highway 420), since the interchange is designed for westward expansion, however this routing has been dropped in favour of a routing directly to Fort Erie.
The route will most likely begin at Peace Bridge or its planned twin bridge in Fort Erie. It will then head west across the peninsula, crossing the Welland Canal and passing south of Hamilton to connect to Highway 403. Later, it is likely that it will either connect with Highway 407 on the northern edge of Burlington. An extension to Highway 401 in Milton will form the first leg of the GTA East-West Corridor.
It is expected that the City of Hamilton will extend the Red Hill Valley Parkway south to connect with the Mid-Peninsula Highway in Stoney Creek, as the Mid-Pen will likely bypass the Lincoln M. Alexander Parkway instead of incorporating it into its routing.