The restructured municipality of Southwest Middlesex was incorporated on January 1, 2001. This amalgamation joined the Village of Glencoe and the Village of Wardsville with the Townships of Ekfrid and Mosa. Southwest Middlesex had a population of 5,860 in the Canada 2011 Census. Southwest Middlesex is located in the southwest corner of Middlesex County, about halfway between London and Chatham.
The township includes the communities of Appin, Ekfrid, Glencoe, Lewis Corners, Macksville, Mayfair, Newbury Station, North Appin Station, North Ekfrid, North Glencoe Station, Riverside, Strathburn, Tate Corners, Wardsville and Woodgreen. It surrounds, but does not include, the independent village of Newbury.