<P> The Nilgiris District is in the southern Indian state of Tamil Nadu . Nilgiri (English: Blue Mountains) is the name given to a range of mountains spread across the borders among 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 2,637 m . The small district is contained mainly within this mountain range; the administrative headquarters is located at Ooty (Ootacamund or Udhagamandalam). </P> <P> Nilgiris District 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 . Tea and coffee plantations have been important to its economy . 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 . </P> <P> The history of peoples settled in the Nilgiri hills has been recorded for several centuries . The Blue Mountains were likely named for the widespread blue Strobilanthes flower or the smoky haze enveloping the area . </P> <P> This area was long occupied by the indigenous tribal peoples of the Toda, Kota, Kurumba and Irula . The Particularly Vulnerable Tribal Groups PVTGs, the dominant land owners of the tribal district . The lower Wynaad plateau in the west of the district had a different tribal population namely Kattunaika and Paniya . The Todas and Kota, who are similar in culture, language and genetic ancestry, were settled across the fringes of the Nilgiri plateau, as sentries to the Central district . They were the ancient agriculturists in the district, cultivating traditional crops such as samai, vathm, ragi . Under British influence they cultivated English vegetables and later moved on to tea . </P>

Why are the nilgiris called the blue mountains
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