Up to 20 km2 of the total area is water, as part of the largest lake in Denmark, Arresø, lies within the municipality.

Its mayor, as of 1 January 2018, is Steffen Jensen, a member of the Social Democrats political party.

Originally a fjord connected to Kattegat, it was landlocked when the land northwest of the lake rose by 5 meters in the last ice age.

The construction of the canal was necessary because the natural stream (Danish:å) from the lake to the fjord was filling up with sand.

The water in the newly built canal was harnessed by a watermill, and the town of Frederiksværk basically was created through industrialization.