The Krishnagiri district has prehistoric importance. Archeological sources confirm the presence of habitats of man kind during Paleolithic, Neolithic and Mesolithic Ages. Various rock paintings and rock carvings of Indus Valley civilization and Iron Age seen in this district support the historical significance of this district. The heart of 'Krishnagiri', 'Hosur' and 'Uthangarai' were known as 'Eyil Nadu', 'Murasu Nadu' and 'Kowoor Nadu' respectively. During Chola period, Krishnagiri region was called 'Nigarili Chola Mandlam' and 'Vidhugadhazhagi Nallur'. Under 'Nulamba' rule it was popular as 'Nulambadi' according to historical sources.
Hero stones were erected for those whose lost their lives in pursuit of adventure. There was a tradition of erecting memorial stones for people who sacrifice their lives for the sake of their kings since 'Sangam Age'. These memorial stones were called 'Navagandam'. Plenty of memorial stones available in this district speak volumes about the valour and virtues of the people. Part of Salem, Dharmapuri, Krishnagiri and Mysore were together named as "Thagadur Nadu" in Sangam Age. "Adhiayaman", the noble king offered 'Karunelli' (Goose Berry) to the great poetess "Avvaiyar" who adorned his court for her long life. Krishnagiri was once ruled by Adhiyaman and hence also known as 'Adhiayaman Nadu'. This region was ruled by Pallavas, Gangas, Nulambas, Cholas, Hoysalas, Vijaya Nagar Emperors, Bijapur Sultans, Wudayars of Mysore and Nayaks of Madurai. This region of Krishnagiri served as gateway of Tamil Nadu and the protective barrier for Sourthern region defending onslaughts from barriers with motives of imperialism and exploitation. Twelve Forts in this region were popularly known as 'Bara Mahal' Forts. These forts have borne the funs of many attacks by Mysore and Andhra rulers. Krishnagiri Fort become the first and forth most defensive place. The majestic fortress built on Krishnagiri hill by the Vijaya Nagar Emperors, stands as testimony still now. ' "Kundani" a place in Krishnagiri District was once the Head Quarters of the Hoysala king 'Veera Ramanathan' in 13th Centuty AD. 'Jagadevarayan', Hoysala kind made'Jagadevi' (one of the 'Bara Mahal' forts) as his capital.
During Mysore war I the British troops passed through Krishnagiri to attack Hyder Ali's Forces at 'Kaveripattinam'. British army was defeated here. In Mysore war II entire region of Salem and Karnataka came under Hyder Ali's control. Hyder Ali fought bravely against the English at Krishnagiri.
In Mysore war II after the "Treaty of Srirangapattinam" entire region of Salem and Barah Mahal were surrendered to the British. In 1792 AD, Captain Alexander Reed became the first District Collector of this region. Under the diplomacy of Robert Clive, the then Governor of Madras Presidency, Krishnagiri became the headquarters of Bara Mahal.
A mint was established at Krishnagiri in 1794 AD. Gold, silver and copper coins were forged here. Rayakottai once the strong hold of British lost its importance for defense by 1880 AD. Many soldiers from Krishnagiri region took part in the world war and lost their lives. Even today a large number of youth from this Krishnagiri district are in the service of our Mother Land. Many patriots and sons of this soil participated in the nations freedom struggle. One among them was the "Wise Old Man, Dr .C. Raja Gopalachari", who
hailed from a small village in this district rose to the highest position in the nation as the first Governor General of independent India and also as Chief Minister.
The historical importance and potential growth in education, economy and tourism of present Krishnagiri made it necessary to create a separate district. Krishnagiri was formed as 30th district by the Government of Tamil Nadu. Krishnagiri district was carved out of Dharmapuri district on 09th February 2004 with five taluks and ten blocks. Thiru. Mangat Ram Sharma, I.A.S. has administered the office as first Collector of Krishnagiri District.