The Ammonites, descendents of Lot, settled in this area in the late 2^nd millennium BC and made Rabbath Ammon (modern Amman) their capital. Rabbath Ammon and the Ammonites bear frequent mention in the Old Testament because they engaged in constant clashes with the neighboring Israelites. In the early 10^th century BC, Israelites conquered the Ammonites and reduced Ammon to a vassal state. In the mid-9^th century BC the Ammonites rewon their independence, but it was quickly lost to the Assyrians and then the Persians.

The Romans changed the name of this city from Ammon to Philadelphia. It became a major city in the Decapolis, with temples, an amphitheater, and other amenities of a contemporary Roman city, and many of these sites are still visible today. Under the Byzantines, Philadelphia was the seat of the bishopric of Petra and Philadelphia. The foundations of many churches built during that period are still intact.