One third of the world's Jews can trace their ancestry to Poland. In the 19th century, Poland had the world's largest Jewish population. (The US has had the world’s largest Jewish population since 1918). In 1931, 3 million out of the 32 million people in Poland were Jewish — 10% of Poland’s population.
Jews first settled in Poland in 7th century, and there were more migrations in 12th through 15th centuries, when Crusades in Western Europe brought persecution. Special laws were passed in Poland to separate the Jewish community — they were self-governing. There were 750,000 Jews in Poland 1764, before the partitions.