Located at a narrow point on Roskilde Fjord, Sundby Færge became the harbour for the nearby market town of Slangerup.

Frederikssund's rapid expansion from a small town at the end of the 19th century is due in large part to the railway connection with Ballerup in 1879 which was upgraded to a frequent suburban service to Copenhagen in 1989.

The recent development of the town center and the old commercial harbour have given Frederikssund a new look which reflects its growing popularity as a residential area with connections to Copenhagen and surroundings.

It has all the facilities associated with a modern Danish town: museums, a public library, supermarkets, a hospital and sports and recreation centers.

Activities range from sailing,[10] rowing,[11] cycling,[12] golfing[13] or gliding[14] to simply sitting out on the main pedestrian street (gågade).

There are several sports clubs and facilities in Frederikssund covering soccer,[15] American football,[16] swimming,[17] basketball, bowling and cycling.