The Wellington District was a historic district in Upper Canada and its successor, Canada West, which existed until 1849. It was formed in June 1840 from townships transferred from certain other districts: For electoral purposes, it was called Waterloo County and the district town was Guelph. Upon the passage of the Act of Union 1840, for electoral purposes Erin Township was attached to Halton County, which became known as the East Riding of Halton, and the remaining townships of Wellington that had previously been part of Halton became known as the West Riding of Halton. When the East and West Ridings were renamed for their respective counties in 1845, the township of Erin continued to be part of Halton for electoral purposes, and the township of Dumfries was similarly included for such purposes in Waterloo. At that time, Waterloo County was declared to consist of the following townships: In 1849, Wellington District was abolished, and Waterloo County remained for municipal and judicial purposes. The territory of the Bruce Peninsula became part of Waterloo in 1849, but was later withdrawn and transferred to Bruce County in 1851.