Union of Lublin

July 1, 1569

The Kingdom of Poland and the Grand Duchy of Lithuania formally merged into the Polish-Lithuanian Commonwealth at Lublin. It became, overnight, one of the largest states in Europe, stretching from the Baltic to the Black Sea and governed by an elective monarchy and a famously fractious noble Sejm. The Commonwealth's elective monarchy and fractious noble Sejm created one of early modern Europe's most unusual polities.