Kasimov is a town in Ryazan Oblast, Russia, located on the left bank of the Oka River. Population: 33,491 ; 35,816 ; 37,521 ; 17,000. The first population of this area was a Finnic tribe called the Meshchyora, later assimilated by Russians and Tatars. The town was founded in 1152 by the Vladimir-Suzdal ruler Yuri Dolgorukiy as Grodets, then Gorodets Meschyorsky. It was included in the Mishar Yurt division of the Golden Horde, but then was sold to Muscovy.