Regional Municipality of York
Post war changes and the rapid urban growth of Toronto led to the shrinking of York County and gave rise to the establishment of the Regional Municipality of York (Regional Municipality of York Act RSO). Following the creation of York Region in 1971, the Town of Markham was incorporated by the larger Township of Markham Village, annexing the smaller villages of Unionville, Ontario and Thornhill, Ontario (portion east of Yonge Street) into the new local government. A new Town Council was created (replacing the councils of Markham Village, Unionville and Thornhill) and led by the following mayors: