The criteria for formation of Indian States is language [and of course politicians these days!]. India became a Republic in the year 1950 and in same year linguistic provinces were formed. The state of Mysore is one such state in south India.
The state of Mysore was created taking into fold various parts of the region, which were ruled by kings. Several districts in, now called North Karnataka and Hyderabad Karnataka were dissolved in the new state. The new state was named after Mysore, which by itself was a princely state.
People of North and Hyderabad area did not accept the name Mysore. People of this region were demanding a change in the name. After prolonged debate the name of the state was changed to Karnataka on November 1, 1973.
Late Devaraj Urs the then Chief Minister of state took this landmark decision. Officially the new state was born on Nov. 1 and on this day every year birthday of the state is celebrated. This is popularly called as Kannada Rajyotsava or Karnataka Rajyotsava. Rajyotsava means "birth of a state".