On August 1, 1927, the uyezds were abolished and Kolpinsky District, with the administrative center in the town of Kolpino, was established. The governorates were also abolished, and the district was a part of Leningrad Okrug of Leningrad Oblast. The station of Popovka became a part of Kolpinsky District. On July 23, 1930, the okrugs were abolished as well, and the districts were directly subordinated to the oblast. On August 19, 1930 the district was abolished. Krasny Bor became a part of newly established Tosnensky District. On August 20, 1935 Krasny Bor, which had the status of suburban settlement, was upgraded to urban-type settlement. During World War II, Krasny Bor was occupied by German troops. In 1943, the Battle of Krasny Bor took place here.