Chennai district, formerly known as Madras district, is one of the 38 districts in the state of Tamil Nadu, India. It is the smallest and the most densely populated district in the state. The district is coterminous with the city of Chennai, which is administered by the Greater Chennai Corporation. It is surrounded by Tiruvallur district in the north and the west, Kanchipuram district in the south-west, Chenglpattu district in the south, and the Bay of Bengal in the east. As of 2011, the district had a population of 4,646,732 with a sex-ratio of 989 females for every 1,000 males. Much of the district's population descended from its settlements in the 1st century CE to the Middle Ages, but the diversity has grown much since then. The district consists of only one civic body, the megacity of Chennai, which forms the core and the most notable portion of the much bigger Chennai metropolis, or officially, the Chennai Metropolitan Area. In 2018, the district's limits were expanded, aligning with that of the newly expanded Greater Chennai Corporation, which had annexed adjacent municipalities. It resulted in the area being increased from to . The district is divided into three revenue divisions and ten taluks. Etymology The name Chennai was derived from Damarla Chennappa Nayak, the father of a general of the Vijayanagar Empire. Geography Chennai district covers an area of 426 km2 located on the Eastern Coastal Plains of India. It is situated on the northeastern corner of Tamil Nadu along the Coramandel coast, a region bounded by the Bay of Bengal and is surrounded inland by the districts of Tiruvallur, Kanchipuram and Chengalpattu. It lies between 12°59' and 13°9' of the northern latitude and 80°12' and 80°19' of the eastern longitude at an average altitude of 6 metres above sea level on a 'sandy shelving breaker swept' beach. Terrain slope varies from 1:5000 to 1:10,000. The terrain is very flat with contours ranging from 2 m to 10 m above mean sea level with a few isolated hillocks in the southwest beyond the district limits at St. Thomas Mount, Pallavaram and Tambaram. The district runs inland in a rugged semi-circular fashion and its coastline is about 25.60 km (2.5% of the total coastline of Tamil Nadu). Because of its strategic location and economic importance, it is referred to as the "Gateway of South India." The drainage system includes two rivers, namely,