The danger of the narrow sound between Trwyn Du (Penmon Point or, more literally, Black Point) and Ynys Seiriol (Puffin Island) was acknowledged in the mid-18th Century, but as is traditional, nothing was done until lives had been lost.
On 17 August, 1831, the paddle steamer 'Rothesay Castle' sank in heavy seas. Of 140 people, daytrippers from Liverpool plus crew, 117 died, prompting the construction of the lighthouse and nearby lifeboat station.