The founder of the princely state of Jamnagar was the Jam
Rawal, who descended on the northern coast of Kathiawar in 1535 A.D. Jam Rawal's
father Jam Lakhaji ruled in Terabanu in Kutch.According to bardic chronicles, Jam Lakhaji
had two cousins Tamachi Deda and Hamirji Jadeja
Nawanagar was founded in 1540 AD by Jam Rawal, a descendant of the Jadeja ruler of Cutch, and was thereafter in an almost constant state of war with its neighbors and with the Mughal Empire. The Walker Treaty of 1807 brought peace to the Kathiawar states for the first time in several generations. Nawanagar came under British protection on February 22 1812.
Nawanagar was one of the first princely states to sign the Instrument of Accession in 1948 after Indian independence. Afterwards, the former ruler Jam Shri Sir Digvijaysinhji served as the first Rajpramukh of Kathiawar, then represented his country at the United Nations.
In 1949 after the former princely states of Nawanagar and Dhrol, Dhrafa Thana and part of Jalia Dewani in Kathiawar merged into new the state of Saurashtra. On June 19 1959, the boundaries of the district were enlarged by the inclusion of the adjoining Okhamandal, and the district was renamed Jamnagar. This district became part of the new State of Gujarat on the division of the State of Bombay on May 1 1960.