The Nilgiris District is in the Indian state of Tamil Nadu. Nilgiri is also the name given to a range of mountains spread across the division between the states of Tamil Nadu, Karnataka and Kerala. The Nilgiri Hills are part of a larger mountain chain known as the Western Ghats. Their highest point is the mountain of Doddabetta, height 2,633 m. The small district is mainly contained within this mountain range, with its headquarters at Ooty (Ootacamund or Udhagamandalam). It ranked first in a comprehensive Economic Environment index ranking districts in Tamil Nadu (not including Chennai) prepared by the Institute for Financial Management and Research in August 2009. As of 2011, the Nilgiris district had a population of 735,394 with a sex-ratio of 1,042 females for every 1,000 males.