Thondaimandalam also known as Thondai Nadu is a historical region located in the northernmost part of Tamil Nadu and the southernmost part of Andhra Pradesh. The region includes the Nellore, Chittoor, North and South Arcot and Chingleput districts of the Andhra and Madras states (now in Andhra Pradesh and Tamil Nadu). It covers the present day areas of Nellore, Chittoor, Vellore, Ranipet, Tirupattur, Tiruvanamalai, Villupuram, Kallakuruchi, Tiruvallur, Kanchipuram, Chengalpattu, Cuddalore and Chennai districts of modern-day Andhra Pradesh and Tamil Nadu. The boundaries of Thondaimandalam are between the river basins of Penna river and Ponnaiyar (Then Pennai) river.
This region covers the North Eastern Agro Climatic zone of Tamil Nadu and the Southern Agro Climatic zone of Andhra Pradesh. The soil types are red sandy loam, clay loam, saline coastal-alluvium. The annual rainfall varies from 850mm to 1400mm as one moves towards the coast. Northeast monsoon is the lifeline of this region with the Lake (Eri) system, canals and tanks harvesting most of the rainfall during the monsoon for use over the next 6-8 months. Paddy, sugarcane, groundnuts, sesame and other horticultural plants are predominantly cultivated here. There are several native breeds found in this region such as Thondaimaadu cattle, Madras Red sheep and other native livestock. There is also a high level of urbanisation and industrialization concentrated around the Greater Chennai area and the Vellore-Ranipet stretch.
