Byelostok (Polish, Bialystok), a town of West Russia, in the government of and 53 m. by rail S.W. of the city of Grodno, on the main railway line from Moscow to Warsaw, at its junction with the Kiev-Grayevo (Prussian frontier) line. Founded in 1320, it became part of Prussia after the third partition of Poland, but was annexed to Russia in 1807, after the peace of Tilsit. Its development dates from 1845, when woollen-mills were built. Since that time it has grown very rapidly, its population being 13,787 in 1857; 56,629 in 1889; and 65,781 in 1901, three-fourths Jews. Its woollen, silk and felt hat factories give occupation to several thousand workers.