The capital of South Sudan is Juba, which was founded 1920. Juba has been the capital since 2011.
Juba is the largest city in South Sudan and functions as: County seat for Juba County.
Juba is located at 4.8594° N, 31.5713° E, at an elevation of 1598' ft.
Source: https://flic.kr/p/VCy7rK