He also wrote the first Lithuanian language history of the Samogitian diocese, that has not lost its scientific value until nowadays. His pastoral and educational work was interrupted by the uprising of 1863–1864 and was made extremely difficult as the Russian government tightened its reins after the collapse of the revolt. Yet these circumstances did not prevent him from following a course which could not but bring him into direct conflict with the authorities. He made every effort to undermine the government’s scheme of Russification. In 1874 Valančius fell ill and died in Kaunas on May 29, 1875. He was interred in the crypt of the Kaunas Cathedral Basilica. His services to the Lithuanian cause were lasting and important, including his opposition to the Russian government and the tactics he employed in resisting its policies, particularly the Lithuanian press ban. He sponsored the illegal practice of printing Lithuanian books in East Prussia and smuggling them into Lithuania by "knygnešiai", which served to stimulate the emergence of the Lithuanian national movement. As an educator, and able Church administrator, historian and ethnographer, and a talented writer, Valančius emerges as one of the most versatile and influential figures in the 19th century Lithuania.