Located in the north-western corner of the Russian Empire, Petrograd was supplied with food via the railway network. With the transportation breakdown caused by the war, it became very difficult to supply such a metropolis. Petrograd stepped into the New Year with its inhabitants infuriated by the long lines in front of food shops. The combination of social unrest and the people's wartime grievances brought about the February revolution of 1917 and the abdication of Nicholas II. At the time of the revolution the tsar was in Mogilev at the army's headquarters. The political and economic crisis continued all through 1917 and in the fall the Bolshevik party led by Vladimir Lenin had captured political power. On October 25 (November 7), 1917 the blank shot of the cruiser "Aurora" gave workers and soldiers the signal to storm the Winter Palace.

Most of the ministers were arrested and 73-years long Communist rule began. At the beginning of 1918 the Civil War (1918-1921) broke out and the revolutionary soldiers and workers of Petrograd became the core of the Red Guard, which later turned into the Red Army. While the fit men were leaving the city for the fronts of the Civil War, a significant portion of the population migrated to the countryside, where families found it easier to provide for themselves. The population dropped from 2.3 million in 1917 to 722 thousand by the end of 1920. By the beginning of 1918 the German troops were so close to Petrograd that the Bolshevik government of Vladimir Lenin decided to move the capital to Moscow, which was still far from the front. Hence Petrograd was left to be just a regional center. Further change occurred when many of the street names were altered according to the revolutionary fashion of the day.