The sixth letter of the St. John to the seven churches of Asia Minor was the letter to Philadelphia. The city lay along a fault line, and is subject to frequent and sometimes powerful earthquakes, making the task of recovering the past in archaeology a difficult one.
The city may have been founded by Eumenes King of Pergamum (197-160 BCE) in the C2BCE, and the name was likely after his brother Attalus (later reigned 159-138 BCE), who through loyalty won the title Philadelphus (brother love). The city was handed over to Roman rule in 133 BCE on the death of Attalus III. The city may well have been founded for a social purpose. Ramsey states that the city was a missionary city from the beginning, founded to promote a certain unity of spirit, customs, and loyalty within the realm.
Located along the Cogamus River, the valley connects with the Hermus River basin to the northwest, where Sardis stood 26 miles away. The valley road was the lifeline connection between the Phyrgian territory to the east and the harbors of the Aegean to the west.
The earthquakes are amply recorded in history, a severe on occurring in 17 CE, which destroyed this city and eleven others. Sardis fared worse from the initial quake, but Philadelphia shook more frequently from severe aftershocks, traumatizing the population.
Strabo noted the city was ever subject to quakes. After Emperor Tiberius aided in their rebuilding, it took the new name of Neocaesarea (New Caesar). Under Vespasian's rule (69-79 CE), it changed names to Flavia. By the third century, paganism had held on in the face of a Christianizing Empire, and the city became known as little Athens for its dedication to deities. None of these names or epithets lasted, and today the modern city is called Alasehir.
Early Church history reveals that Ignatius made a visit to the city on his way to his martyrdom in Rome, and sent a letter to the church there.