After the Mahabharat War; India was divided into small and large provinces called Janapadhadas and Mahajanpadhas. 16 Mahajanpadhas became prominient after the Mahabharat War. These were: Kuru, Panchala, Kosal, Kashi, Magadha, Anga, Kamboja, Vajji, Malla, Vatsa, Chedi, Matsya, Surasena, Ashvaka, Avanti, and Gandhar. Most of them were subsequently absorbed into Magadha empire. Sreemad Bhagwad records the dynasties that ruled major proviences of: Kamboja, Gandhar, Sindhu, Kuru, Sursena, Matsya, Avanti, Panchal, Kosal, Vrijji, Vatsa, Chedi, Kashi, Magadha, Malla, Anga, Asmaka.
After Yudhishthir 28 Kuru kings ruled over Kuru-Panchala area.  Nichakshu, the fifth king after Parikshit, moved the capital from Hastinapur to Kausambi after a heavy flood on the Ganga. There is definite archaeological evidence of a massive flood in the thick clay soil. The last king of this dynasty, Kshemak was overthrown by Sahadeva of Magadha dynasty.
32 Magadha kings (only 22 are named) ruled for 1000 years.  Bimbisar was the most remarkable king of this dynasty. He extended the boundaries of the Magadha kingdom upto Nepal. He built the city of RajGriha (Rajgir in Bihar). Gautam Buddha and Mahavir Jain, preached their teachings during his time. His son Ajatshatru conquored Kosal by defeating Prasenajit. (Prasenajit was a decendant of Rama. He ruled over Kosal from Shravasti.) Ajatshatru founded the city of Patalipura (Patna). The last Magadha king Puranjaya was killed by his minister Shunak, whose son Pradyot initiated the Pradyot dynasty.
5 Pradyot kings ruled for 173 years. Pradyotas ruled from Avanti. Their kingdom covered central and western India. It was prosperous due to the trade with Mesopotamia. Their main sea port was Bharoch (Gujrat).
Shishungas defeated Pradyots to establish their rule. 10 Shishunga kings ruled for 360 years.
Mahapadma-Nanda, an illegitimate son of the last Shishunaga emperor Mahanandi, established the Nanda dynasty. 9 Nanda kings ruled for 100 years. The Nandas maintained a huge army, and hence had to rely on heavy taxation. Chandragupta Maurya overthrew this dynasty with Chanakya's help, and established the Maurya dynasty.
During this time dams were constructed on rivers for water storage and irrigation. Rainfall was measured. Silver coins were issued by the rulers to facilitate trade.
- Swayambhu - Dr P V Vartak