The British North America Act, 1867 designated the electoral districts to be used in elected the members of the House of Commons. By virtue of the size of its population, the County of York was divided into a number of ridings, instead of being allocated one seat in the House of Commons like many other counties. The initial boundaries of the North Riding of York were defined in 1859 to consist of the Township of King, Whitchurch, Georgina, East Gwillimbury and North Gwillimbury, and the villages of Aurora, Newmarket and Holland Landing. Over time, the boundaries were adjusted as the City of Toronto expanded, and as the population of the area grew. In 1882, the riding was redefined to consist of the townships of King, East Gwillimbury, West Gwillimbury, North Gwillimbury and Georgina, and the villages of Holland Landing, Bradford and Aurora. In 1903, the north riding was redefined to consist of the townships of Georgina, East Gwillimbury, North Gwillimbury, King, and Whitchurch, the towns of Aurora and Newmarket, and the villages of Holland Landing, Stouffville and Sutton. In 1924, York North was defined as consisting of all that part of the county of York north of the southerly boundary of the townships of Vaughan and Markham. In 1933, it boundary of the townships of North York and Whitchurch, excluding the village of Stouffville. In 1947, it was redefined to consist of that part of the county of York lying north of the line being the southerly boundary of the township of North York, Yonge Street and the southerly boundary of the township of Markham. In 1952, it was defined as consisting of that part of the county of York lying north of Highway 7, excluding the town of Woodbridge. In 1966, it was defined as consisting of a north-central section of the Borough of North York in Metropolitan Toronto, the Town of Richmond Hill, the Township of Markham excluding the Village of Stouffville, and part of the Township of Vaughan. In 1976, it was redefined to consist of the Towns of Markham, Richmond Hill and Vaughan in the Regional Municipality of York. In 1987, it was redefined to consist of the towns of Aurora, Richmond Hill and Vaughan, and the southern part of the Township of King. In 1996, it was redefined to consist of the towns of East Gwillimbury, Georgina, and Newmarket, as well as the part of King north of Side Road 18. The electoral district was abolished in 2003 when it was redistributed between the electoral districts of Newmarket—Aurora, Oak Ridges—Markham and York—Simcoe.
