Short answers, pulled from the story.
Leningrad Oblast was officially established on the 1st of August 1927 by All-Russian Central Executive Committee resolutions. The initial total area exceeded four times the modern entity size covering regions now belonging to Murmansk, Vologda, Novgorod, and Pskov Oblasts plus Saint Petersburg itself.
The Neva River flows from Lake Ladoga to the Gulf of Finland in just 74 kilometers while the Volkhov River hosts archaeological sites dating back to the end of the Weichselian glaciation. The Oredezh River cuts through Siversky and the Luga and Narva rivers define borders with Estonia within this territory.
Peter the Great conquered the territory from Sweden during the Great Northern War which lasted from 1700 to 1721 and founded Saint Petersburg amidst the land in 1703. Alexander Menshikov served as Governor General when most of the territory organized into Ingermanland Governorate in 1708.
The Winter War began on the 30th of November 1939 when the Soviet Union attacked Finland. Moscow Peace Treaty in 1940 granted territories including the Karelian Isthmus to the Soviet Union after Finnish residents evacuated hastily to inner Finland.
By 2021 census population reached 2,000,997 after rising from 1,716,868 recorded in 2010. Russians made up 93.7 percent of ethnic composition that year while surrounding population remained non-Russian until the 20th century historically.