A 'baltic port', is any port on the Baltic Sea, which is situated between Scandinavia and northern-central Europe. Oslo, Stockholm, Helsinki, Gdansk, Rostock and Copenhagen are all Baltic ports.
St. Petersburg is a port on the Baltic Sea
Kiel There are several notable port cities in Germany that are on or near the Baltic Sea, but Kiel is the largest and most profitable.
Gdansk in Poland
Lithunia's main port is Klaipeda, on the south eastern side of Baltic Sea
There is the Russian Enclave of Kaliningrad on rhe Baltic, and St Petersburg which is on the Gulf of Finland, a branch of the Baltic Sea
Latvia, the Republic of Latvia.
Gdańsk.
Both St Petersburg and Kaliningrad
Estonia, Latvia and Lithuania
If you mean Tsar Peter the Great, then St Petersburg
The Latvian Socialist Soviet Republic.
Because Peter the Great wanted a trading port through which he could easily trade with Western Europe's maritime nations and he wanted a port that wouldn't be iced up in winter. A seaport on the Baltic coast fit both requirements.