Upon the founding of West Germany in 1949, the US High Commissioner was headquartered in a small castle in Bonn-Mehlem. It was at one time owned by the Deichmann family. They were prominent Cologne bankers who, since 1836, had summered in the meadow on the Rhine, where, in 1911, they renovated their estate. Deichmannsaue Castle, after restructuring and renovation measures, later became the headquarters of US High Commissioner John Jay McCloy. In 1951, a modern, 21,000 square meter office building was constructed next to the castle for the staff of the High Commission for Occupied Germany (HICOG).
A special housing tract was also installed in Plittersdorf for HICOG staff and their families. The 1953 edition of Baedeker’s travel guide referred to the tract as “Little America.” The houses were all outfitted with electric cookers, refrigerators, and “hot water available around the clock.” The guide also noted that the tract had its own shopping street, a pavilion-style school, a gym, a swimming pool, a clubhouse, a restaurant and a cinema.
The HICOG, however, ceased to function in 1955. As early as May 1952, all three High Commissioners – the American, the British and the French – hammered out the details of a treaty with the German government during a two-day meeting at Deichmannsaue Castle, which was also attended by German Chancellor Konrad Adenauer. The resulting General Treaty (Deutschlandvertrag), which was signed on 26 May 1952 in the parliamentary chamber of the Bundesrat and was a first step toward rescinding the Occupation Statute, came into effect in 1955, by way of the Bonn-Paris conventions. As a result, the office of the Allied High Commission moved from Petersberg to block 3 of the HICOG building in 1952.