The riding is in its third stint as a district represented in the House of Commons.
Originally established in 1968, it existed until 1978, when it was split.
It returned from 1988 to 1997 and was reestablished in 2004.
When the ridings were redistributed in 2012, Innisfil was removed from York-Simcoe riding and put into Barrie-Innisfil.
York-Simcoe stretches into four municipalities: East Gwillimbury, Georgina, King and Bradford West-Gwillimbury.
Its southerly border is Hwy. 9 in King and Green Lane and Davis Drive in East Gwillimbury.
The riding includes all of Bradford West Gwillimbury and Georgina.
Demographics according to the 2011 census:
Area: 844 square kilometres
Population density: 112.1 per square kilometre