St. Petersburga is the singular genitive of St. Petersburg.

St. PetersburgN

Rare in texts

Norwegian Bokmål

St. PetersburgNx

Nordsamisk-norsk ordbokdict-sme-nob/src/N_Propgeo_smenob.xml:43983Edit on GitHub Suggest

Case	Sg
Gen	St. Petersburga / St. Petersburg
Ill	St. Petersburgii
Loc	St. Petersburgas