In ancient legend, Howth was home to a chieftain called Croimhthain whose fort (Irish: Dún Croimhthain) gives the name Dungriffan to a local road.
Viking raids began in 819. Later, a major battle between Anglo-Norman and local forces (Irish and settled Viking) occurred here, near the rivulet called the Bloody Stream, the leader of the winning party, Armoricus Tristram, being granted Howth (as far as Kilbarrack where the road from Baldoyle reached the sea, including the near waters) as his estate.
Tristram took on the name of the saint on whose feast day the battle was won, and built his first castle near the harbour - and the St. Lawrence link remains even today.
Howth was a trading port from at least the 14th century, with both health and duty collection officials supervising from Dublin, although the harbour was not built until the early 1800s.
A more recent legend concerns the pirate Grace O'Malley, who was rebuffed in 1576 while attempting a courtesy visit to Howth Castle, home of the Earl of Howth. In retaliation, she abducted the Earl's grandson and heir, and as ransom she exacted a promise that unanticipated guests would never be turned away again. She also made the Earl promise that the gates of Deer Park (the Earl's demesne) would never be closed to the public again, and the gates are still open to this day, and a place set at table for unexpected guests.
In the early 18th century, Howth was chosen as the location for the harbour for the mail packet(postal service ship). One of the arguments used against Howth by the advocates of Dún Laoghaire was that coaches might be raided in the badlands of Sutton! (at the time Sutton was open countryside.)[2] However, due to silting, the harbour needed to be frequently dredged to accommodate the packet and eventually the service was relocated to Dún Laoghaire. George IV visited the harbour in 1821.
In 1914, thousands of rifles were landed at Howth by Robert Erskine Childers for the Irish Volunteers. Many were used against the British in the Easter Rising and the subsequent Anglo-Irish War.