BIALYSTOK, a town of Poland, capital of the province of the same name in 53° 8' N. and 10' E., on the main railway line from Warsaw to Leningrad. Founded in 1320, it became part of Prussia after the third partition of Poland, but was annexed to Russia in 1807. Its development dates from 1845, when wool len mills were built; its population was 13,787 in ; 56,629 in 1889; and 91,335 in 1931, about three-fourths being Jews.