Following the third partition of the Polish–Lithuanian Commonwealth in 1795, Prienai was invaded and occupied by Prussia. Prussia ruled there during the years 1795-1807 and made Prienai part of New East Prussia. At the end of the eighteenth century, Prienai underwent rapid economic growth. During that time a glass factory and a paper mill, one of the largest in Lithuania, were established near the town. The paper mill produced extraordinary high quality white, coloured and wrapping paper, which was often exported to cities as distant as Warsaw and Saint Petersburg.