Indicates the jurisdiction between York Region and neighbouring regions. The municipal boundaries define the limits of the Region's nine area municipalities: Aurora, East Gwillimbury, Georgina, King, Markham, Newmarket, Richmond Hill, Whitchurch-Stouffville and Vaughan, as well as 'Chippewas of Georgina Island First Nation.' Reassessment of the Regional Municipality of York Act statutes took place in 1970.