In 1876, The harbour was the landing-site of the first Atlantic Ocean single-handed sailing, west-to-east, starting from Gloucester, Massachusetts, by Alfred "Centennial" Johnson.

[1] Abercastle is an old trading harbour which exported local slate and grain, limestone, butter, honey, corn, and some coal.

[2] Alfred Johnson landed at Abercastle on Saturday, August 12, 1876, after 66 days sailing from Gloucester, Massachusetts, becoming the first person to make the single-handed Atlantic crossing.

[3] A plaque made of Welsh Slate is on the quay wall near the slipway and was unveiled by Alfred Johnson's grandson, Charlie Dickman on 17 October 2003.

[7] The harbour faces northwest and is therefore sheltered from south-westerly gales, providing a safe haven for the local fishing fleet.