Western District was one of four districts of the Province of Quebec created in 1788 in the western reaches of the Montreal District and partitioned in 1791 to create the new colony of Upper Canada. Known as Hesse District (from Hesse in Germany) until 1792, it was abolished in 1849. The district originally consisted of that part of Upper Canada west of a line running north from Long Point on Lake Erie, in the region now referred to as Southwestern Ontario. The district town was Sandwich, later renamed Windsor.
In 1798, the district was reorganized to consist of the counties of:
At the same time, parts of the district were separated to create a new London District.
In 1847, legislation was initiated to create a new Kent District; however, facilities at the designated district town of Chatham needed to be built. The creation of the new district was not completed.
In 1849, the district was replaced by the United Counties of Essex and Kent.
In 1853 Waterloo County was created on the eastern boundaries of the former Western District.