From the Wikipedia page 
Juba County was an administrative area in Central Equatoria state, South Sudan. It was the largest county in Central Equatoria and one of the largest in the entire region of Equatoria. Its county seat was Juba, the state capital of Central Equatoria and the national capital of the Republic of South Sudan. Its population according to the disputed 2008 census conducted by the Republic of the Sudan, prior to South Sudanese independence, was 372,413. In 2015, the county was turned into the state of Jubek.