For centuries Siemiatycze remained property of several Polish-Lithuanian magnate families. The town, conveniently located along the Bug River, and near local administrative centers at Drohiczyn and Mielnik, became a popular market place, where farmers sold their produce. Disastrous Swedish invasion of Poland (1655-60) did not bring widespread destruction to Siemiatycze. The town continued to prosper, at the expense of other municipalities of the region of Podlachia, all of which burned to the ground by the Swedish, Transilvanian and Russian invaders.