The name of Seaforth is thought to come from the Old Norse sæ-fjord, sæ-ford, "sea inlet". It was recorded as Safforde "sea ford" in 1128, suggesting Old English name origins. Another theory for the name of the area is that it was taken from Seaforth House, named after Francis Mackenzie, 1st Baron Seaforth, who built the mansion in 1813 for his daughter and her husband, Sir John Gladstone, father of William Ewart Gladstone, four times Prime Minister of the United Kingdom.
Seaforth joined Crosby Municipal Borough in 1937, having previously been part of Waterloo with Seaforth urban district. The whole of Crosby became part of the new Metropolitan Borough of Sefton on 1 April 1974.
From 1918 to 1950 Seaforth was within the Parliamentary constituency known as Waterloo, a safe seat for the Conservative Party, and then until 2010 within the Crosby constituency, whose MP from 1997 to 2010 was Claire Curtis-Thomas, of the Labour Party. Prior to her election the Crosby seat was generally considered a Conservative Party stronghold, like its predecessor seat, with Tory MPs elected at every election, except for the 1981 Crosby by-election, when Shirley Williams of the Social Democratic Party was elected. As a result of boundary revisions for the 2010 general election, the Crosby constituency was abolished and Seaforth was included in the expanded Bootle constituency, represented by the Labour MP Joe Benton.
Motorcycle speedway racing was staged at Seaforth Stadium in the late 1930s. Greyhound racing also took place until the 1960s
- Kenny Everett, radio presenter and comedian, born in Seaforth
- William Ewart Gladstone, prime minister
- Edmund Knowles Muspratt (1833—1923), chemical industrialist
- Max Muspratt (1872–1934), chemist & politician
- Julia Solly (1862–1953), British-born South-African feminist
- Nessie Stewart-Brown (1864–1958), feminist
- "Seaforth Barracks". British Commission for Military History. Retrieved 26 May 2014.
- "Obituary:Kenny Everett" The Independent 5 April 1995 Retrieved 27 July 2010
- Liverpool Echo, January 28, 2008. Retrieved 19 August 2011