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.
List of ambassadors of the United States to South Sudan
The government of the United States recognized South Sudan on its independence day, July 9, 2011. On the same day, the existing U.S. consulate (accredited to the Republic of Sudan) in the capital Juba was upgraded to embassy. R. Barrie Walkley, the U.S. Consul General in Juba was appointed to serve as Chargé d'Affaires pending the appointment of a U.S. Ambassador to Juba.