The Kano Chronicle highlights an ancient history dating to around 999 AD of the Hausa Sahelian city-state of Kano, with other major Hausa cities (or Hausa Bakwai) of Daura, Hadeija, Kano, Katsina, Zazzau, Rano, and Gobir all having recorded histories dating back to the 10th century. With the spread of Islam from the 7th century AD, the area became known as ''Sudan'' or as ''Bilad Al Sudan'' (English: Land of the Blacks; Arabic: بلاد السودان). Since the populations were partially affiliated with the Arab Muslim culture of North Africa, they began Trans-Saharan trade and were referred to by the Arabic speakers as ''Al-Sudan'' (meaning "The Blacks") as they were considered an extended part of the Muslim world. There are early historical references by medieval Arab and Muslim historians and geographers which refer to the Kanem-Bornu Empire as the region's major centre for Islamic civilization.