The northern plain has been constituted by the interaction of the three major river systems, which are — the Indus, the Ganga and the Brahmaputra along with their tributaries. This fertile plain is formed by the deposition of alluvium in a vast basin lying at the foothills of the Himalayas over millions of years. This area is around 7 lakh sq km. wide. The plain being about 2400 km long and 240 to 320 km broad, is a densely populated physiographic division. Approx. 45% population of India lives in the northern plains. This part of India is agriculturally productive because it is rich in soil cover combined with an adequate water supply and a favourable climate. The rivers coming from the northern mountains are involved in depositional work. In the lower course, due to the gentle slope, the speed of the river decreases, which results in the formation of riverine islands. In their lower course, the rivers split into numerous channels due to the deposition of silt. These channels are known as distributaries.

The Northern plain is spread over states like north Rajasthan, Punjab, Haryana, Delhi, Uttar Pradesh, north Bihar, West Bengal and Assam. The Northern plain can be divided into three parts- Punjab Plain, Ganga Plain and Brahmaputra Plain.