On August 1, 1927, the uyezds were abolished and Oranienbaumsky District, with the administrative center in the town of Oranienbaum, was established. The governorates were also abolished, and the district was a part of Leningrad Okrug of Leningrad Oblast. It included parts of former Trotsky Uyezd. On July 23, 1930, the okrugs were abolished as well, and the districts were directly subordinated to the oblast. On August 27, 1939 Bolshaya Izhora was made an urban-type settlement, and on September 17, 1939 Oranienbaum became the city of the oblast significance and ceased to be a part of the district. Between August 1941 and January 1944, during World War II, the western part of the district was occupied by German troops. The eastern part was not occupied and served as the Oranienbaum Bridgehead to protect the city of Leningrad. On February 23, 1948 the town of Oranienbaum was renamed Lomonosov to commemorate Mikhail Lomonosov, and the district was renamed Lomonosovsky. On December 10, 1958 Sosnovy Bor was granted the urban-settlement status. On February 1, 1963 Lomonosovsky District was abolished and merged into Gatchinsky District; on January 13, 1965 it was reestablished. On November 22, 1966 Lebyazhye was granted urban-type settlement status. On April 19, 1973 Sosnovy Bor became a town of oblast significance and ceased to be a part of the district. As a result of a sequence of administrative reforms, the town of Lomonosov was transferred to the federal city of Saint Petersburg, and thus Lomonosovsky District is the only district in Russia which has its administrative center lying in a different federal subject.