The idea of providing cheap and healthy homes for the poorest part of the city's work force originated among local politicians and medical doctors during the 1853 Copenhagen cholera outbreak which killed approximately 5,000 citizens. A major reason for the outbreak was the dismal conditions in the poorest parts of the city which suffered from overcrowding and lack of proper sanitary services. Copenhagen's population had almost doubled since 1800 but the city had still not been allowed to expand beyond its old fortification ring.