The Siedlce Regional Museum covers local history from prehistoric times through the 20th century, with particular attention to the town's role as a regional center under various political regimes — Polish-Lithuanian Commonwealth, Prussian partition, Russian Empire, interwar Poland, and the Nazi occupation. The collection includes archaeological finds, period documents, and material culture from the region.
The museum's documentation of Siedlce's Jewish community before the war is handled with care and depth. Siedlce had a large and long-established Jewish population, most of whom were murdered at Treblinka in 1942, and the local museum's commitment to preserving this history makes it a meaningful stop even for visitors without a specific interest in Jewish history.