That is the quiet puzzle at the centre of Mullingar's Sessions House: a structure that administered justice and county business for generations, yet whose exact position has been lost to time, leaving only documentary traces scattered across land surveys and grant confirmations.

The Sessions House appears in the 1641 Survey of Mullingar, which places it on the south side of what is now Pearse Street, then the Main Street of the town. The survey is granular in the way that property records of the period tend to be, describing not the building itself but what lay beneath it: two cellars and a garden plot occupied by a man named Charles Whyte, bounded to the east by a house once associated with Donnogh O Shiel, to the south by the vicar's garden, and to the west by the dwelling of one Elizabeth Guires. By 1667, a confirmation of a land grant to Sir Arthur Forbes under the Acts of Settlement and Explanation, the legislation used to redistribute land after the Cromwellian period, still described the site in terms of those same cellars and the garden above them. The building itself was apparently functional but undistinguished. In 1682, the antiquary Sir Henry Piers wrote that the old sessions house was 'very narrow and inconvenient in all respects', and noted that a new one was already being constructed, 'very large and spacious according to the modes of modern architecture'. Piers also observed that Mullingar served as the county's principal venue for assizes and sessions, four annual fairs, and all major public gatherings, suggesting the town's legal infrastructure carried considerable regional weight. Whether that new late seventeenth-century courthouse occupied the same ground as its predecessor, or shifted to somewhere near the present courthouse site, remains unresolved.