In addition to fish the sea also provides amber, especially from its southern shores. The bordering countries have traditionally provided lumber, wood tar, flax, hemp, and furs. Sweden had from early medieval times also a flourishing mining industry, especially on iron ore and silver. Poland had and still has extensive salt mines. All this has provided for rich trading since the Roman times.

In the early Middle Ages, Vikings of Scandinavia fought for power over the sea with Slavic Pomeranians. The Vikings used the rivers of Russia for trade routes, finding their way eventually all the way to Black Sea and southern Russia.

Finland and the Baltic states were the last in Europe to be converted into Christianity in the Northern Crusades: the former in the 12th century by the Swedes and the latter in the 13th century by the Germans. First the Livonian Brothers of the Sword and then the powerful German Teutonic Knights held the Baltic countries and fought with Danes and the Swedes, while the foundations of Russia were being laid in Novgorod.

Later on, the strongest economic force in Northern Europe became the Hanseatic league, which used the Baltic Sea to establish trade routes between its member cities. In the 16th and early 17th centuries, Poland, Denmark and Sweden fought wars for Dominium Maris Baltici (Ruling over the Baltic Sea). Eventually, it was the Swedish empire that virtually encompassed the Baltic Sea. In Sweden the sea was then referred to as Mare Nostrum Balticum (Our Baltic Sea).

In the 18th century Russia and Prussia became the leading powers over the sea. Russia's Peter the Great saw the strategic importance of the Baltic and decided to found his new capital, Saint Petersburg at the mouth of the Neva river at the east end of the Gulf of Finland. There was much trading not just within the Baltic region but also with the North Sea region, especially the eastern England and the Netherlands: their fleets needed the Baltic timber, tar, flax and hemp.

During the Crimean War a joint fleet of Britain and France attacked Russian fortresses by bombarding Sveaborg that guards Helsinki and Kronstadt that guards Saint Petersburg and destroying Bomarsund in the Åland Islands. After the unification of Germany in 1871, the whole southern coast became German. The First World War was fought also on the Baltic Sea. After 1920 Poland returned to the Baltic Sea, and Polish ports of Gdynia and Gdan'sk became leading ports of the Baltic.

During the Second World War Germany reclaimed all of the southern shore and much of the eastern by occupying Poland and the Baltic states. In 1945 the Baltic Sea became a mass grave for drowned people on torpedoed refugee ships. As of 2004, the sinking of the troopship Wilhelm Gustloff remains the worst maritime disaster of all time, killing (very roughly) 9,000 people.

After 1945 the sea was a border between conflicted military blocks: in case of military conflict in Germany, in parallel with a Soviet offensive towards the Atlantic Ocean, communist Poland's fleet was prepared to invade Danish isles.

In May 2004, the Baltic Sea became almost completely a European Union internal sea when the Baltic states and Poland became parts of the European Union, leaving only the Russian metropolis of Saint Petersburg and the enclave of Kaliningrad as non-EU areas.

The Baltic Sea starts to get very rough with the October storms. These winter storms have been the cause of many shipwrecks, like for example the Estonia in 1994. But thanks to the cold brackish water where the shipworm cannot survive, the sea is a time capsule for centuries-old shipwrecks. Perhaps the most famous one is the Vasa.