Database: The Provinces of Settsu, Izumi, and Kawachi

These three ancient provinces of Japan which border on current Osaka Bay and are all located in the Kinai region formed a single province in archaic Japan, Ōshikōchi, which was divided into three parts in 719. To the east, was the province of Kawachi which corresponds today with the eastern part of Osaka Prefecture. In the center, the province of Izumi, which was part of Kawachi until 757 before being separated. To the west, the province of Settsu straddled the current prefectures of Osaka and Hyogo (where the current city of Kobe is located).

This entire region was one of the major centers of development in the archaic period. Notably, it contains the largest ancient tumuli in the country, with the one attributed to Emperor Ōjin (Ōjin ryô) in Kawachi and the one attributed to Nintoku in Izumi. The ancient palace of Naniwa was located in what is now the center of Osaka city. Situated around the ancient delta of the Yodo River, these regions were the natural outlet to the sea for the capital Kyoto, and the gateway to the Kinai for all goods transiting through the Inland Sea during the Middle Ages. This is why, with the development of trade, especially with China, the port of Sakai experienced significant growth during the 15th and 16th centuries. Located on the border between the provinces of Settsu and Izumi, Sakai (which means 'the Border') became a prosperous merchant city that governed itself and was compared by the first Portuguese travelers with the great free cities of Italy. It was near Sakai, in Ishiyama, that the fortress temple of Hongan-ji was built. This was the center of the Ikkō sect of the Amidists, which controlled many armed peasant leagues in the Kinai and beyond. Furthermore, Osaka Castle, a new fortress, was built at Honganji by Hideyoshi. At the foot of Osaka Castle a new city prospered and became the economic center of the country in the 17th century, to the detriment of nearby Sakai.