Llanfyllin was named after the seventh century St. Melyn, the first baptist in Britain (`Mewn Llwyn? ? `Saint in the Pool?), to whom the local church is dedicated (NPRN 400220). An Iron Age enclosure (NPRN 306784) overlooks the Cain valley, and it is possible that the town, on the bank of the River Cain, had an early medieval origin, though there is no evidence of continuous occupation. The town was incorporated in 1293, when it received its charter granting a weekly market and annual fair from Llewelyn ap Grufydd ab Gwenwynwynt. Llanfyllin, together with Welshpool, is one of only two Welsh towns to have received its charter from a native ruler. It was later granted privileges and immunities by Edward I, and Charles II confirmed the foundation charter.
There are a number of malt kilns in the vicinity of Llanfyllin, malt having been its principle trade for much of its history; there were also tanneries, corn mills (NPRN 40192 & 40197) and a woollen mill (NPRN 41041). A quarry (NPRN 308770) was established to the north west of the town. The weekly market was held beneath the Town Hall (NPRN 32054), which also served as a National School and was where all public business took place. The former workhouse (NPRN 32044) was recently restored and now serves as a focal point of the community.

Source: Lewis, S. A Topographical Dictionary of Wales, 1833
RCAHMW Inventory Documents

K Steele, RCAHMW, 5 January 2009