Ostrowiec was one of main centers of the Revolution in the Kingdom of Poland (1905–1907). On December 27, 1905, the so-called Ostrowiec Republic was established, and for two weeks, the town and the county were ruled by the Polish Socialist Party, headed by Ignacy Boerner. The Republic was ended after the arrival of two infantry regiments of the Imperial Russian Army. The Ostrowiec Works was severely damaged during World War I, and on November 3, 1918, newly established Polish authorities took control over Ostrowiec. In the Second Polish Republic Ostrowiec developed, due to its location in Central Industrial Area. The town belonged to Opatow County, and before World War II its population was app. 30,000. In 1937 it was officially named Ostrowiec Swietokrzyski. Earlier on, the names Ostrowiec Kielecki and Ostrowiec nad Kamienna had been used.