History of Gujarat
As per Records, Jam Rawalji built Jamnagar in around A.D. 1519. Kshatriyas of Jadeja empire of Kutchh, crossed little Rann of Kutch with an army, defeated Jethwas, Dedas, Chavadas and formed Navanagar State. The region was called Halar from the name of Halaji, Son of Gajan, the ancestor of Jadeja Empire .

The historians say that Jam Rawalji built the arched gate of Jamnagar in approximately 1519 AD. The Kshatriyas of the Jadeja dynasty came from the Kutch along with their army by crossing the small desert from the Kutch border, established the Navanagar state by defeating the Jethva, Deda, Chavda and Wadher branches of Rajput. This region was named as Halar on the name of Halaji, the son of Gajan, the predecessor of the Jadeja dynasty and since then, this region is known as Halar.

The boundary of the ancient Halar state is comprised of the gulf and desert of Kutch on the north, Desert of Okha Madhi and the Arabian Sea on the west, the princely states of Rajkot, Dhrol, and Gondal and Sorath region on the east. The climate of Halar is temperate. Being situated under the effect of the winds flowing from the Arabian Sea and the Gulf of Kutch, the temperature here remains low. Consequently, the atmosphere during the mid-summer also remains pleasant. Wind - speed here generally remains from 50 to 55 KMPH. Navanagar means a big princely state of Halar region in Kathiyawad and Navanagar means today’s Jamnagar.

Looking to the history of construction of the ancient Navanagar, this town seems to be founded on confluence of the river Nagmati and Rangmati. The confluence point of the river Nagmati and the Ranmati always kept changing. Before foundation of the Navanagar, sea shore was there at the present confluence point of these two rivers and there was a prosperous port of ‘Nagna’ or ‘Nagnes’. Mainly the sea exploring communities like Bhoi, Kharva, Koli, Vagher were hebitating in the village adjacent to the port. Jam Rawal won this port by killing the Ruler Nag Jethva of the Jethva dynasty. It appears that this port might have been survived for a long time and its trade was also going on even after Jam Rawal won this port.