On 2 October 2015 the President of the Republic of South Sudan, Salva Kiir Mayardit decreed the creation of the new Jonglei State along with 27 other states replacing 10 previous states in the country. The earlier Jonglei state comprised of three counties of Bor, Twic East and Duk. In May 2016, the new Jonglei was reorganized into 17 new counties. The current governor of Jonglei State is Maker Thiong Mal.
Former Jonglei was the largest state by area before reorganisation, with approximately 122,581 km2, as well as the most populous according to the controversial 2008 census conducted during present-day South Sudan’s second period of autonomy. Bor is the capital of the state.
Jonglei seceded from Sudan as part of the Republic of South Sudan on 9 July 2011. In the 21st century. In May 2016, the new Jonglei was reorganized into 17 new counties as follows:
FORMER BOR COUNTY 1. Bor South County 2. Bor Gok County 3. Bor East County 4. Makuach County 5. Bor Center County 6. Bor West County 7. Athooch County 8. Bor North County.
FORMER TWIC EAST COUNTY 1. Twic South County 2. Twic Center County 3. Twic North County 4. Kongor County.
FORMER DUK COUNTY 1. Duk Padiet County 2. Duk Payuel County 3. Duk Panyang County and Duk Pagak.

The main rivers are the White Nile, which flows in the western part of the state, and the Pibor River and its tributaries which flows in the central-east draining 10,000 km to white Nile.