In the early 1900s, Białystok was reputed to have the largest concentration
of Jews of all the cities in the world. In 1931, 40,000 Jews lived in the city,
nearly half the city's inhabitants. The city is the seat of the Roman Catholic
Archdiocese of Białystok. Pope John Paul II on 5 June 1991, during a visit to
Białystok, announced the establishment of the Archdiocese of Białystok which
ended the period of the temporary church administration of the portion of the
Archdiocese of Vilnius that had, after World War II, remained within the Polish
borders. The city is also the seat of the Białystok-Gdansk Diocese of the
