 The city of Fredrikstad was founded in 1567 by King Frederick II, and established as a municipality on 1 January 1838 (see formannskapsdistrikt).The rural municipality of Glemmen was merged with Fredrikstad on 1 January 1964.The rural municipalities of Borge, Onsøy, Kråkerøy, and Rolvsøy were merged with Fredrikstad on 1 January 1994.