In the mid-1800s, the peasants had to stop letting their cattle graze on the west coast of Amager, which back then was protected by the Mejlgård Dyke between what is now Finderupvej and Bella Center Copenhagen. The military set up a target range on Amager Fælled and the coastal area was designated as a security zone.
Even at this time, land-reclamation projects in these shallow waters between Zealand and Kalvebod Strand beach were being considered. Building dykes would make it possible to deepen the channel, gain more fertile land, and provide the military with larger areas.
However, legislation authorising reclamation of Kalvebod Strand etc. was not passed until 1939, as an employment project to reduce the high unemployment of the time. Because of the German occupation of Denmark in 1940, and to stop unemployed Danes being sent to Germany on forced labour, the work was started the year after.
In 1943, the about 14-km-long and four-metre-high dyke was finished, and canals and ditches were dug, so that water could be pumped out from the around 20-km2 area, which was drained in a matter of months. During the work, thousands of birds settled in the reclaimed area, and the south-westerly part became a bird sanctuary in 1952. It was listed in 1990. In the late summer of 2012, the coastal protection was fortified by a 5.9-metre-high dyke behind the old one.