After the Polish-Russian War, Ostrołęka became one of the most destroyed cities. Although it suffered great losses, Ostrołęka stayed a district city of Płock's Province. Ostrołęka's economy greatly declined. Nearly all the city's craftsmen became bankrupt. Only products of Ostrołęka's amber works were still supplied all over Europe. Ostrołęka got refunds from the Tsar's Treasury. However, it took a long time before it rose from its downfall. In 1847 a monument commemorating Russian Army's victory in the battle of Ostrołęka was raised on 26 May 1831. At the time of January's insurrection, no battles took place nearby Ostrołęka, as the Tsar placed a quite large Russian detachment in the city worrying of another Kurp Uprising. In 1864, after the Russian government's order, the Benedictines left Ostrołęka and the monastery buildings were placed under the parish-priest authority.