A blue plaque was unveiled to commemmorate the engineer who designed and built the amenity Alexander Nimmo.
The Irish Times reports that altogether, he built some 30 harbours and piers around the coast of Ireland and many of them were in Connemara.
The harbour and lighthouse at Dunmore East were completed around 1821. Costs rocketed during construction; what had begun as a £20,000 project ended up costing £108,000.
It was designed for the mail boats that came from Milford Haven in South Wales, but within about 10 years it had silted up and the mail service was transferred to nearby Waterford.
Local councillor Pat Fitzgerald said he hoped the harbour would continue to serve the community into the future:
He says he hopes a festival will take place later in the summer to celebrate the harbour.