The urban development of the area in the early 1900-s, had a direct link to the cholera epedemic. Like many illnesses, cholera thrives where people live close together in with poor hygienic conditions. In the 1850s, around 220.000 people lived on the 32 acres that made up Copenhagen at the time. This equals around 6000 people per acre. Furthermore, the only drinking water available came from leaky wooden pipes. These pipes were polluted with the mixed wastewater from the streets.
A doctor, Emil Hornemann, was put in charge of dealing with the epidemic. He claimed that fresh air would help the patients to recover, and therefore relocated the sick to tent camps outside of the city. It seem to work. Even though the illness kept coming back every year, it faded. The success of this approach initiated a series of hygienic reforms, such as preventing people from living in basements, or attics, or prohibiting children under the age of 10 from working in factories.
Additionally, some of the highest populated districts of Copenhagen were demolished, including the district in the picture above. Out of the many, many people dislocated from the city center, some would become the very first inhabitants of the area of the park, as some of the first newly invented social housing areas would grow around Grønningen.
The actual shape of the park, the isolated green surface without intended use , in itself is a trace of the concept of the social housing, concieved from early 1900. Access to a green open area was the core of this concept and reason to move the large, challenged population out of urban areas like in the image above.