History of Sudan
The modern Republic of Sudan was formed in 1956 and inherited its boundaries from Anglo-Egyptian Sudan, established in 1899. For times predating 1899, usage of the term "Sudan" for the territory of the Republic of Sudan was somewhat anachronistic, and may have referred to the more diffuse concept of the Sudan.
History of South Sudan
In 2005, Comprehensive Peace Agreement, mediated by the Intergovernmental Authority on Development (IGAD), as well as IGAD-Partners, a consortium of donor countries, was signed in Nairobi and autonomous Government of Southern Sudan was formed. This agreement lasted until 2011, when South Sudan declared independence.