Princely state
The Dumraon Raj was a feudal principality in the Bhojpur region ruled by the Ujjainiya dynasty. The principality was founded when Raja Horil Singh founded a separate capital for himself in the town of Dumraon. The name Dumraon Raj came from its capital town. 
It was a zamindari state during British era. During the time of Indian independence, Dumraon Raj covered an area of 2,330 km2 which stretched from Buxar district in west Bihar to Ballia district in the Purvanchal region of Uttar Pradesh. In Ballia district, Dumraon Raj covered rights of more than 70 villages which are located on the banks of the Ganga river.
The royal family of Dumraon is also the main patron of the famous Brahampur fair.
History.
The founders of Dumraon Raj were Ujjainiya Rajputs who traced their origin to the Parmar rulers of Malwa who moved to Western Bihar in the 14th century. In the medieval era, the head seat of Ujjainiyas was Bhojpur.
Raja Mukutman Shahi who ascended the throne of Bhojpur in 1601 was highly unpopular amongst his kinsmen and thus he was forced to abdicate in 1607 in favour of his nephew.
In 1607, Raja Narayan Mal came to the throne of Bhojpur and he was recognised as the new ruler of Bhojpur by Mughal Emperor. He received the title of Raja and was granted the rank mansab of 5000.
In the Battle of Buxar 1607-1608, he routed the Chero and Munda forces. The "Rajas" of Bhojpur were known for their rebellious behaviour against Mughal rule and during the family feud of the ruling family of Bhojpur, the Mughal governor found this opportunity to completely sack Bhojpur. The territory of Bhojpur was sacked in the year 1699 and it came under direct Mughal rule.
One of the descendants of Raja Narayan Mal, Raja Horil Singh, established himself separately and built the capital town of Dumraon in 1709. He got recognised to rule his dominion under Mughal rule. This is how Dumraon Raj came into existence. However, the rulers of Dumraon Raj were only recognised as feudal rulers.
Rulers.
The rulers of Dumraon Raj used the title Raja and later Maharaja.
References.
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