The Rev. Alban Thomas Jones Gwynne had amassed an extensive local landholding through his marriage. In 1807 he secured the Act of Parliament he needed to develop a port at the mouth of the River Aeron. He began building the harbour at once, and the harbour worked - steam ships still visited until the 1920s, and shipbuilding became a major local trade through the 19th century. The town behind the harbour grew more slowly. Gwynne died in 1819 with much of the residential plan unbuilt. It took his son, Colonel A. T. J. Gwynne, picking up the project after his mother's death in 1830, to bring in the architect who would finish the design: Edward Haycock Senior, a Shrewsbury man with a busy practice across Shropshire, the Welsh Borders and South Wales. Haycock drew a grid plan with a central square. Leases on the plots were sold from the 1830s on, and the town began to look like a town.

Alban Square - the principal square that anchors the whole design - is named for the elder Gwynne. Haycock's terraces around it are simple by Regency standards: two-storey, slate-roofed, plainly detailed in cut stone. The Pevsner architectural guide to Carmarthenshire and Ceredigion finds the buildings too small in scale to give the central green a real sense of enclosure. But it acknowledges that the present appearance entertains. Sometime in the 20th century the houses were painted in pastel colours - pinks, blues, yellows, mints, the occasional lavender - and the effect is what most visitors remember. The Pevsner authors call this no authentic restoration. It is also, recognisably, what makes the town a destination. Aberaeron looks like nowhere else within fifty miles, and the colours are why.

Two Aberaeron institutions survived into the modern era from the harbour's busiest days. The first is the Aeron Express: a hand-powered aerial cable ferry, originally built in 1885 by Captain John Evans after a flood took out the road bridge, used to shuttle workers across the harbour mouth between the Liverpool and Birkenhead quays. The original ran into the twentieth century. A re-creation operated as a tourist attraction from 1987 until 1994, when health and safety regulations closed it down, but the concrete footings are still on both quays, and locals still talk regularly about restoring it. The second institution is the Hive on the Quay, a converted wharf-side building where the Davies family has been making honey ice cream for thirty-five years, sweetened with local honey rather than sugar, served in the parlour above the harbour where shipwrights once worked. The flavour combinations rotate: chocolate, hazelnut, elderflower, gooseberry. The honey base does not.

Aberaeron was always meant to be administratively important as well as commercially useful. Haycock's design included a Town Hall, completed in 1846, which was upgraded to County Hall when Cardiganshire's administration consolidated here in 1910. Today the county council's headquarters at Penmorfa still anchors local government for Ceredigion. The 1911 branch railway from Lampeter brought the railway era to the town just in time for the harbour trade to fade, and passenger services ceased in 1951. Dylan Thomas knew the town - the Dylan Thomas Trail passes through, on its way from Talsarn to New Quay where he wrote much of Under Milk Wood. There are 248 listed buildings inside the small community, an extraordinary concentration. The annual festival of Welsh ponies and cobs is held each August in Alban Square Field, and a life-sized statue of a cob stallion, sculpted by David Mayer, was donated to the town in 2005. The architecture has even featured on British postage stamps. Two centuries after a clergyman drew lines on a map of empty coast, the town he invented is one of the most photographed small ports in Wales.