High Quality Content by WIKIPEDIA articles! Merseyside ( /ˈmɜrzisaɪd/) is a metropolitan county in North West England, with a population of 1,365,900. It encompasses the metropolitan area centred on both banks of the lower reaches of the Mersey Estuary, and comprises five metropolitan boroughs: Knowsley, St Helens, Sefton, Wirral, and the city of Liverpool. Merseyside, which was created on 1 April 1974 as a result of the Local Government Act 1972, takes its name from the River Mersey.