Almost immediately after its creation, some sort of merger was advocated, with "Wentworth" being among some of the candidate names for the new megacity, despite the City of Hamilton functioning as the metropolitan core for the Region as a whole.

The Region provided policing, social services, and public transit (by taking over Hamilton Street Railway), while the lower-tier provided Fire Services and Recreation Services; although, both tiers shared the responsibility for maintaining Roads and Water.

Near the end of its existence, the Regional Chair was chosen by Direct Election.

The Regional Municipality of Hamilton–Wentworth was created by Act of the Legislative Assembly of Ontario in 1973, which took effect on January 1, 1974.

This was part of a broader series of municipal reorganizations in urban and rural Ontario, and was also the fate of Metropolitan Toronto, the Regional Municipality of Ottawa–Carleton, Chatham-Kent, Prince Edward County, and many others.