Archaeologists have found agricultural settlements in Bihar from before 2000 B.C. Cities emerged in the area around the 500's B.C. The ancient Indian state of Magadha dominated the region during this period. It became the centre of a succession of powerful kingdoms. Some of the kings were outstanding administrators.

Bimbisara (reigned 544-493 B.C.) unified and strengthened his kingdom and maintained good relations with neighbouring states and contacts as far afield as Taxila in the northwest. His successor Ajatasatru (reigned 493-462 B.C.) was another outstanding ruler. These and other Magadha kings expanded the territories they ruled to form a major Indian empire.

During the period of Magadha rule, the region of Bihar experienced changes in social and economic life. As towns grew in number and size, trade and commerce developed. There were also changes in religion. The Magadha rulers supported the emerging religions of Buddhism and Jainism. There are many places in Bihar that are associated with Gautama Buddha, the founder of Buddhism, and Vardamana Mahavira, the founder of the Jain faith.

Toward the end of the 300's B.C., a new empire emerged in the Bihar region, as Chandragupta Maurya overthrew the last of the Magadha rulers. Chandragupta Maurya reigned from about 321 B.C. to about 298 B.C. and laid the foundations of the Maurya Empire. This was the first empire to unite most of India under one ruler.
The early Magadha kings had their capital at Rajagriha, 100 kilometres west of the modern city of Patna. Stone walls with a perimeter of about 40 kilometres surrounded Rajagriha.

When Chandragupta Maurya came to power, he moved the capital to Pataliputra, the site where Patna now stands. Pataliputra had the shape that Patna has today - a long, narrow city stretching along the bank of the Ganges River. Chandragupta's grandson was the great emperor Ashoka, who became ruler of all India except the south. A pillar bearing one of Ashoka's edicts has a capital with lions facing the four directions of the compass.

For 600 years after the death of Ashoka in 232 B.C., the Bihar region was ruled by fairly insignificant clans. Then the Guptas came to power. These kings encouraged a flowering of Hindu culture, known as the classical period, in the A.D. 300's and 400's. The poet and dramatist Kalidasa and the astronomer Aryabhata were great intellectuals of this period. The Guptas expanded their territory despite defeat by the Huns.

Turks and Afghans arrived and defeated the Hindu rulers in 1197. From that time the influence of Muslim political power in Bihar was very strong. The Delhi sultans and a succession of local Muslim rulers, independent of Delhi, controlled the region until the 1500's.
Sher Shah Suri, Bihar's ruler, won fame for his defeat of the Mughal emperor Humayun in 1539. Sher Shah became emperor of northern India. Bihar became Mughal territory during the reign of Akbar (1556-1605). Muslim place names, such as Aliganj and Hajipur, are evidence of 500 years of Muslim political dominance.

The Mughals retained Bihar until the British won the Battle of Buxar in 1764. At that time, Bihar was still part of Bengal, but later the two regions were separated. Bihar became a province under British rule and declined into poverty.
The British (United Kingdom) government's policy of granting land ownership to local zamindars (tax collectors) meant hardship for Bihar's peasants. The region became a breeding ground for resistance to the British and for nationalist movements and rebellions.
Bihar took its present form at India's independence in 1947. It lost two districts, Purnea and Manbhum, to West Bengal during the 1956 reorganization of India's states.