Beneath the present surface, and long since demolished, stood a succession of market structures that once formed the commercial core of the east town, on the Westmeath side of the Shannon. Nothing of them survives above ground today, yet the documentary record is unusually precise, and what it describes is a place that changed its physical form several times across three centuries before disappearing entirely.

The earliest market house on the site was a timber structure, built around 1586 to 1587 after the crown granted a lease to a soldier named John Rawson. The terms were specific: the market place measured roughly 18 metres by 14 metres, Rawson was to build immediately on an existing stone foundation, and the lease required him to leave room for two carts to reach the High Street and a cartway around the building. The lease also carried a striking restriction, barring him from transferring the property to anyone who was not of English descent on both sides or born within the English Pale, a boundary that defined the area of Ireland under reliable crown control. Earlier leases from 1578, granted to Edmund O'Fallon and Henry Brande respectively, fix the market place's position relative to the Dublin Gate, the north gate, and the friary, giving a clear sense of how it sat within the walled town. In 1703 the timber house was replaced by something considerably more substantial: a three-storey arcaded stone tholsel and market house, a tholsel being a combined tollhouse and civic hall common in Irish and English towns, topped with a tower and a cross. Its location is recorded on Thomas Sheppard's 1784 map of Athlone. By 1837 it was gone, demolished without replacement.

Athlone also had a second market place on the Roscommon side of the river, opposite the castle, though no market house was ever built there. In 1619 the crown licensed a weekly Saturday market and an annual fair on that side of town, beginning on the Monday after the Epiphany, with a court of pie-powder attached. A pie-powder court, whose name derives from the French for dusty feet, was a summary tribunal held on fair days to settle disputes among travelling merchants on the spot. The profits from the Roscommon market were to be split equally between the crown and the corporation, with the town sovereign acting as assay-master and justice of the peace across both counties.