The district is situated on the northern bank of the Elbe River. While Pinneberg is the smallest district within Schleswig-Holstein, it has the most inhabitants. Due to the growingHamburgmetropolitan area the population is still increasing. The district consists mainly of the northwestern suburbs of Hamburg. Although the district of Pinneberg is only connected to the sea through the Elbe, the archipelago of Heligoland became a part of this district in 1932.