In 2010, residents of our Republic celebrated the 90th anniversary of its creation. This book is dedicated to this significant date and selective history of Petrozavodsk and Karelia for the period from 1917 to the 50s. XX century, i.e. Soviet Karelia. The story is interesting and glorious, but sometimes difficult and sometimes tragic. To this end, I chose several, in my opinion, key moments in the history of the Republic: 1. Revolution and Civil War in the North and Karelia; 2. Collectivization and collective farm construction; 3. Canadian and American Finns in the Republic; 4. Construction of BBK and Solovetsky special purpose camps; 5. Soviet-Finnish War 1939-1940; 6. Great Patriotic War in Karelia; 7. Restoration of Petrozavodsk.