The region covered by present-day Theni District was sparsely populated before the 1900s. In 1886 Mullaperiyar dam project bought some part of the water from Periyar River downhill to the Cumbum Valley and merged it into the Mullayar River. This project helped more people to settle down in Cumbum Valley. Also to be noted that Theni was itself was a small though lesser-known town by the 1900s. After the Mullai-Periyar merger project, many people from nearby arid regions (Sivakasi, Kovilpatti, Virudhunagar, Sattur and several nearby towns) settled in Cumbum Valley (present day Theni District). So there was influx of people by the 1890s to 1920s. Bodi and Periyakulam were famous places at that time. Later Theni developed rapidly due to commerce.