Portpatrick's exposed situation on the North Channel between Scotland and Ireland made the development of a harbour difficult.
John Smeaton (1724-92) designed a new harbour and proposed breakwaters to protect it, although only one was completed. In 1802,
Thomas Telford (1757 - 1834) advised that further improvements were necessary. Another noted civil engineer John Rennie (1761 - 1821), assisted by his son Sir John Rennie (1794 - 1874), deepened the harbour and built the North and South piers in 1821. The North Pier was lost to the sea in 1839. The Inner Basin was constructed 1861-63 but the harbour had become almost disused by 1873 and lighthouse from the South Pier was dismantled and re-erected in Colombo (Sri Lanka). Ownership of the harbour passed to the Portpatrick Community Trust in 2012 and it is now home to pleasure craft and a few fishing boats.