Karnataka is a state in South India. It was created on 1 November 1956 with the passage of the States Reorganisation Act, and this day is annually celebrated as Karnataka Rajyotsava (Formation Day). Originally known as the State of Mysore, it was renamed Karnataka in 1973. It is the land of the Kannadiga, Tuluva, Konkani, and Kodava peoples. With over 61 million inhabitants as of 2011, Karnataka is the ninth largest state by population in India. Kannada is the most widely spoken and official language of the state. The two main river systems of the state are Krishna and its tributaries (Bhima, Ghataprabha, Vedavati, Malaprabha, and Tungabhadra) in the north, and the Cauvery and its tributaries (Hemavati, Shimsha, Arkavathi, Lakshmana Thirtha and Kabini) in the south. Both these rivers flow eastward and fall into the Bay of Bengal. With an antiquity that dates to the paleolithic, Karnataka has also been home to some of the most powerful empires of ancient and medieval India. The philosophers and musical bards patronised by these empires launched socio-religious and literary movements which have endured to the present day. Karnataka has contributed significantly to both the Carnatic and Hindustani forms of Indian classical music.