The Bayajidda legend, recorded by 19th-century chroniclers such as the Kano Chronicle and recited at the courts of the Hausa emirs, tells of a Baghdadi prince — Abu Yazid, Hausa-ised as Bayajidda — who fled west across the Sahara, arrived at Daura, killed the snake Sarki that had been blocking the town's well, married the queen Daurama, and fathered seven sons who became the founders of the seven Hausa Bakwai ('the genuine seven'): Daura, Kano, Katsina, Zaria (Zazzau), Gobir, Rano and Biram. A parallel set of Banza Bakwai ('the bastard seven') — Zamfara, Kebbi, Nupe, Gwari, Yauri, Ilorin and Kororofa — were said to descend from a concubine.
The city-states emerged historically between the 10th and 14th centuries on the savannah plains south of the Sahara, each fortified with massive earthen walls (Kano's ramparts, begun under Sarki Gijimasu c.1095 and completed under Muhammad Rumfa in the 15th century, reached 17 metres in height and 14 kilometres in circumference and still stand). They were governed by a Sarki (king) advised by a council including the Galadima, Madawaki and Wambai. Islam reached Kano under Sarki Yaji (r. 1349–1385) through Wangara traders from Mali, and Sarki Muhammad Rumfa (r. 1463–1499) institutionalised it with the building of the Friday mosque, the establishment of the Kurmi market, and the invitation of the Maliki jurist Muhammad al-Maghili from Tlemcen, whose treatise The Obligations of Princes became the constitutional text of Hausa kingship.
The Hausa cities were Africa's textile capital — Kano indigo-dyed cloth was traded as far as Tripoli, Tunis and Timbuktu — and the leather of Sokoto and Kano was exported across the Sahara to Morocco, where European traders mislabelled it 'Moroccan leather'. They were also major slave-trading polities: Kano, Katsina and Zazzau raided southward into the Middle Belt and Bauchi for captives.
The city-states never federated. Their rivalries — Kano–Katsina, Gobir–Zamfara — and their failure to enforce strict Sharia on a syncretic Muslim peasantry created the opening for Shehu Usman dan Fodio's jihad of 1804–1808, which dethroned every Hausa Sarki and replaced them with Fulani emirs answerable to the Sokoto Caliphate. The Hausa monarchies survive today as Fulani-Hausa emirates: the Emir of Kano, the Emir of Katsina, the Emir of Zaria and the Emir of Daura are direct successors to the Sarkis of the pre-jihad cities, but the ruling houses are Fulani, not Habe (the original Hausa-speaking dynasties).