The town of Harlech was planned in conjunction with Harlech Castle (NPRN 93729), which was to be built on the site of an earlier Celtic fortress and form a link in the chain of castles built by Edward I across North Wales following the late thirteenth century conquest of the country. Building began in 1283, and advanced with such speed that only a year later a royal charter was issued granting the town the right to hold a weekly market and four annual fairs.
While Harlech Castle reached enormous proportions, the town remained extremely modest in size, serving primarily as an administrative centre rather than residential, with the Hundred Court and County Sessions meeting there for several centuries. There are records of a borough mill in the locality by 1305, and of a town hall, all physical traces of which are now lost, but tax records indicate that the town had few occupants. In 1404 the majority of the residences were burned by the forces of Owain Glyndwr as he occupied the castle.
During the later Middle Ages the town adopted a `sub-urban? character, based upon small scale rural industries, and this largely survives to this day. While the weekly market no longer takes place, there remain a number of annual fairs in the town. The beautiful location of Harlech and the grandeur of its castle ensure a thriving tourist trade.

K Steele, RCAHMW, 29 December 2008
 

Halsalm, Orbach and Voelcker have written about some of the more modern buildings which can be found in the town. The Spar now occupies a two-storey building built in c.1830, whilst down the steps next to the Spar Harlech Pottery can be found. It is a late eighteenth centurey building of squared rubble with sash windows.' Harlech Institute and Old Library, on Stryd Fawr, was built in 1908 'possibly by O. Morris Roberts & Son, in rock-faced stone with shouldered gables’ Halsalm, R., Orbach J., and Voelcker, A., (2009) The Buildings of Wales: Gwynedd  Halsalm, R., Orbach J., and Voelcker, A., (2009) The Buildings of Wales: Gwynedd (p. 615)