Jerash stands in a fertile valley with springs and evidence of human occupation extending back into prehistory. The urban center known in Greek and Roman sources as Gerasa developed during the Hellenistic period, possibly under Seleucid influence, though foundation traditions are uncertain. Roman general Pompey incorporated the region into Rome's eastern sphere in 63 BCE. Gerasa became associated with the Decapolis, a group of cities linked by Hellenistic culture, trade, and Roman provincial administration rather than a formal league with one fixed membership and constitution.

The city prospered especially in the first through third centuries CE. A monumental oval plaza negotiated the different alignments of the sanctuary of Zeus and the long colonnaded Cardo. Temples of Zeus and Artemis, theaters, baths, fountains, markets, bridges, gates, and streets displayed civic benefaction and Roman urbanism adapted to local topography. Hadrian's visit in 129 or 130 encouraged construction of a triumphal arch south of the walls. Greek inscriptions, local cults, Semitic names, and imported architectural language reveal interaction between Mediterranean forms and regional society.

Christian communities transformed Gerasa in late antiquity. Churches with mosaics rose within and beside older civic buildings, while festivals and administration changed. After Muslim armies took the region in the seventh century, occupation continued under Umayyad rule; houses, workshops, and a mosque demonstrate that the city was not instantly abandoned after Rome. A devastating earthquake in 749 caused extensive collapse, and political and economic shifts reduced the settlement. Medieval occupation returned in limited forms, while the modern town grew east of the ancient core from the nineteenth century.

Travelers recorded visible ruins before systematic excavation began in the 1920s. Archaeologists cleared streets and monuments that had been buried or incorporated into later landscapes. Numerous columns have been re-erected, stage fronts and walls partially reconstructed, and masonry consolidated. The South Theater's lower stage level, for example, includes restoration and continues to host performance. Jerash is therefore exceptionally extensive but not untouched or wholly standing. Original pavements, wheel ruts, foundations, columns, and decorated blocks coexist with anastylosis, replacement material, modern paths, and event infrastructure.

Jordan's Department of Antiquities manages the archaeological park and museum, with ticketed entry and inclusion in the Jordan Pass. Jerash remains on Jordan's World Heritage Tentative List rather than the inscribed UNESCO list, an important distinction from some common descriptions. The ancient ruins sit beside a living modern city and host the Jerash Festival and other activities. Their value lies in continuity across Hellenistic, Roman, Byzantine, Umayyad, medieval, archaeological, and contemporary phases. Interpretation must present restoration honestly while preserving the remarkable urban relationships that make Gerasa legible on the ground.