In 1938, adventurers from Leyte in the Visayas set foot on this area. Honorato Elegio, Gregorio Magallanes and Fernando Magno Sr., were the first migrants to have come to this place where Mansaka, who were headed by Tribal Chieftain Bugani Tunglason, were the aborigines. Since then, more migrants came lured by the abundance of nature that made it truly a magnet for those who searched for better, greener pastures.

On June 18, 1955, Mainit was created into a barangay named by Bugani Tunglason because of the hot river. And Mr. Fernando Magno, Sr. was appointed as the first Tentiente del Barrio.

To date, it is the largest barangay of the municipality of Nabunturan in terms of area, and it has the largest population next to the Poblacion. In Purok 9 lower Tindalo, it has a sub-station of the National Power Corporation that provides power at 138k watt in its main line and 60k watt in its minor lines. It has its own elementary school, high school, and public market apart from the typical health center,day care center, Barangay Hall and multipurpose building. Offices of the barangay government is established at different buildings that barangays usually don’t have. To the barangay is a jeepney route that starts at Poblacion and ends there as its final destination and back again. 

At the moment under the leadership of Punong Barangay Alfredo B. Abenales, barangay Mainit is in boom of processing gold and other associated metallic minerals, hence the barangay government has designated a mineral processing zone.