The Nilgiris lies in the Western Ghats, which is one of the major mountain range in India. Most of the mountain ranges above 5940 ft, where the Doddabetta ranges at 8649 ft. The Nilgiris formerly spelt as Neilgheerries latterly meas the Blue Mountains.
The Nilgiri measuring about 2500 sq km lie between 110 10’ and 110 30’ N latitude and between 760 25’ and 770 25’ longitude. Nilgiri is one of the ancient mountain, Geographically. The bedrock of the hills consists of rocks date back to the Palaeolithic era. The mountain spread across the borders among the states of Tamilnadu, Karnataka and Kerala.
The district covered with jungled steep escarpments and foothills. It comprises an upper and lower plateau. The two parts quite dissimilar in their climate, flora and fauna and in general characteristics. District classified into upper pleatue(Nilgiri Plateau), lower Plateau (wynaad)Sigur and the outer slopes facing the plains.  The district consist of  grassy undulating hills, divided y narrow valleys which consist of steam. Also the shoals in the hollows of the hillsides.
Admistratively Nilgiri is one of the district of 32 district of Tamilnadu. Bounded by Mysore district of Karnataka, in north wynaad district of Kerala in west, Coimbatore district in South and Erode of Tamilnadu and Chamarajanagar of Karnataka in East. The district is divided into Six Taluks viz Ootacamund, Coonoor, Kotagiri, Kundha, Gudalur and Pandalu. Contains four Panchayat unioins two Municipalities, wellington Cantonment and Aravangadu Township. There are 35 Village Panchayat and 13 Town Panchayat.
The Original inhabitants of the Nilgiris are the Badagas, Kota, Toda Kurumba and Irulas. Each indigenous people have their own ecological niche.
Nilgiris was a part of Mysore Province till 19th century. After the death of Tipu sultan the British ceased the Nilgiris and merged the Nilgiris with Madras Province. After Independence the Nilgiris was permanently merged with Tamilnadu when the linguistic states were formed.
Many Neolithic monuments could be found in nilgiris, mostly in Badaga Villages where Badagas considered it as Sacared. Badagas says that these monuments are built by their ancestors. They offer regular pojas to the monuments.

Early History
Precious Stone Trade was carried on between Indus Valley civilization(5000 B.C) and the Nilgiris. At Mohanja Daro and Harappa, "The beautiful green amazon stone could be found near Doddabetta, Nilgiris." Probably Doddabetta derived from Badaga Words ("Dodda - Big"+ "Betta - Mountain", "Doddabetta"),

Mouriyan Dynasty
During Mouriyan period(321 B.C - 184 AD) Buddhist Monks entered Nilgiris to spread Buddhism among the Badagas in Nilgiris, where came the tree worship among Badagas. Nilgris was under Hegemony of Mouriyans. 

Kadamba Dynasty
During Kadamba(2AD - 6AD) period, the land revenue and other taxes were collected from Badagas of Nilgiris. Food grains were measured by "Kolaga" and "20 Kolaga" a "Kanduga", "Kolaga" in Badaga is "Koga". Still the word Koga is used by Badaga people. Food grains were paid as a tax to Kadambas

Ganga Dynasty
Later, during Ganga Dynasty(200 AD to around 930AD), Nilgiri was under Ganga Rule. Says, can find a Fort near Hullical Droog. A Badaga Chief has built the Fort. Gangas Ruled Nilgirs No doubt Nilgiris was an administrative unit of Gangas.
Raja Raja Cholan I, The entire south India came under his control as such the Nilgirs and Kongu Area. Was crossing eighteen forests for the sake of his emissary to visit Nilgiris

King Kala
In 1116 A.D. a Badaga King called Kalaraja was ruling Nilgiris. Vishnuvardana of Hoysala Kingdom of Karnataka was the first king to invade Nilgiris, sent his army and tried to threaten the Badagas and ordered to obey him.
The Brave Badaga King, Kalaraja refused his order and fought with him. Kala was Killed   in the war with Hoysalas. Three inscriptions refers to Kala's rule from his fort in Kukal Village. It testified that King Kala was ruling from 1116 AD and implied that his ancestors had been living here centuries earlier. King Kala was killed in a "Dhandu(war). The Nilgiris came under Hoysala Empire after Kala Raja's death.

Hoysala Dandanayaka
Perumal Dandanayaka, the great minister of Ballala III of Hoysalas was the builder of Dandanayakakottai. His son Madhava Dandanayaka  was ruling Padinalkunadu in the south of Mysore. According to Nicholson, author of Coimbatore Manual(1898), Dandanayakakottai was constructed in1338 by Madappa Dandanayaka who was ruling Nilgiris and Wyanad. He was followed by his son Ketaya Dandanayaka ruled in1321 and by Singaya Dandanayaka in 1338. They are the Subduer of Nilgiris. Descendants of these were the Nava Dandanayakas, nine brothers and chief among them was Perumal Dandanayaka.

Vijayanagara Empire
Later in 13th century, the Hoysala Kingdom was defeated by Vijayanagara Empire. So Nilgiri came under Vijayanagara Empire. The tax was collected at Dandanayaka Kotae, Which was build during Hoysalas, Which is near Gopichettipalayam, Submerged in the river Bavani. The history of Nilgiris during Vijayanagara period was under two different poligars. The Ummathur and Danayakas. The Ummathur chief held the taluks of Ootacamund and Gudalur while Danayakas held the taluks of Kotagiri and Coonoor adjoining the Coimbatore District.

Ummattur Chiefs
During 15th and 16th  centuries Ummattur chiefs ruled Nilgiris and Terakanambi near Myore as a subordinate of Vijayanagara empire. They rebelled against he suzerain power to become independent but in vain. Nelekota their important fort in Nilgiris. Certain Ummattur chiefs bore the title Nilgiri Sadaran(Ruler of Nilgiris).

Sultan Rule
Later the Dandanayakas in Dandanayakakottae was dependent on Nayakas of Madurai. Hyder Ali attacked the King Virapandya Devan at Dandanayakakottae  and captured the Dandanayakakottae. In the inscriptions its mentioned Nilagiri Sadaran Kotae(the fort of conqueror of Nilgiris). Dandanayakakottae villages along with Nilgiri ws called as Oduvanganadu. Hyder Ali was succeeded by Tipu Sultan.

The British
Later in 1799, British defeated Tipu Sultan and captured Nilgiris. Mountain tracts were unknown to them till 1818, however tax were collected from Dandanayakakotae. Until then Nilgiris was a part of Mysore Province. Later British merged Nilgiris with Madras province after defeat of Tipu Sultan. In Post-Independence Nilgiris was permanently merged with Tamilnadu.

European Visit
Even before Britishers arrived to Nilgiris, a Portuguese Priest called Rev. Jocome Fierier visited Nilgiris in 1602. He did not stay in Nilgiris. He returned back and informed that he found a group Badagas and Todas.
In 1800 Buchanan made a one-day visit to Nilgiris, partly describes its climate, forest collection, swidden farming and cattle keeping of the Nilgirians and the lifestyle of Badagaru
In 1812, Williams Key visited Nilgiris from the plains of Coimbatore. Wish and Kindersley visited Nilgiri in 1818 by the Dandanayakakottae, Denad route.
Later in 1819, John Sullivan came to Nilgirs through Dandanayakakotae-Denad route reached Dimbatti, a Badaga Village, with help of a Badaga elder named Muthiya Gowder. He first reached Kotagiri, then Ootacamund. An inscription about Muthiya Gowder who guided the Sullivan still exist in Milidane village near Kotagiri. After his arrival The Nilgiris was declared as summer capital of Madras Province.
Sullivan constructed the stone house in 1822. In 1868 Nilgiris was separated from Coimbatore and placed under a commissioner and assistant commissioner. Later commissioner became the Collector.
After Independence the Nilgiri was a part of the composite Madras presidency and after reorganization of states under linguistic basis in 1956, Nilgiri became a part of (Madras State) Tamilnadu.