Trafford is a metropolitan borough of Greater Manchester, England. With an estimated population of about 211,800 in 2006, it covers 41 square miles (106 km2) and includes the towns of Altrincham, Partington, Sale, Stretford, and Urmston. The borough was formed on 1 April 1974 by the Local Government Act 1972 as a merger of the municipal boroughs of Altrincham, Sale, and Stretford, the urban districts of Bowdon, Hale, and Urmston and part of Bucklow Rural District. All were previously in Cheshire, apart from Stretford and Urmston which were in Lancashire. The River Mersey flows through the borough, separating North Trafford from South Trafford. Historically the Mersey also acted as the boundary between the historic counties of Lancashire and Cheshire.