Bremen is a port city of northern Germany on the River Weser; with its satellite port of Bremerhaven, on the Weser estuary, it forms the Freie Hansestadt Bremen (the Free & Hanseatic City of Bremen), the smallest Land (state) in the Federal Republic of Germany. It retained this independence from surrounding Lander as during the Allied occupation of Germany following World War II it was a detached portion of the American Zone: the US forces wished for a seaport under their own administration, and the rest of the North Sea and Baltic Sea coasts of Germany were under British or Soviet control. The state of Bremen has a population of 646,000 (2006) of whom 546,000 live in Bremen, the rest in Bremerhaven. Bremen is currently ruled by left-center SPD and Leftist Environmental Alliance '90/The Greens. The mayor Jens Böhrnsen is a member of SPD.