Sean McLachlan recently wrote a couple of interesting posts about the Vikings in North America for the travel blog Gadling. One was on L'Anse aux Meadows, the only confirmed Viking settlement in the New World. The other is on the controversial Kensington Runestone and other purported Vikings traces in the U.S. These runestones are problematic to say the least and may be modern forgeries.
There is a whole subculture in the United States of trying to prove that various ancient cultures arrived in the New World before Columbus. One of the more popular theories is that Saint Brendan voyaged to the New World.
Saint Brendan lived from about 484-577. Not much is known about his life for certain. One later account written in the ninth century, Voyage of St Brendan the Navigator, tells a fantastic tale of his seven-year journey to the Isle of the Blessed and back. This isle was supposedly far to the west out in the Atlantic. During their voyage, the saint and his companions meets devils, Judas, and sea monsters, and have many adventures. Time and against the saint protects his followers by calling on God.
While it seems like a Christian fable or morality tale, some people, especially Irish-Americans, think it proves that the early Irish visited the New World. There's no archaeological evidence for this, however and there is no mention of it in any of the Irish records besides the fantastical tale of Saint Brendan. One would think that Irish monks risking life and limb to preach to the native Americans would write an account of their exploits.
Back in 1976, adventurer Tim Severin decided to prove that Saint Brendan could have made the voyage. He constructed a currach, the traditional Irish boat of the times. These boats come in all sizes and are made of leather lashed onto a wooden frame. Severin's boat was 36 feet long and had two masts. A model is below. he and his crew sailed this unlikely craft all the way from Ireland to Newfoundland.
This was certainly an impressive feat. Showing that Brendan could have made it, however, doesn't prove that he did. Severin had the advantage of knowing where he was going!
While Severin was a serious investigator, the same can't be said for some of those searching for the early Irish in the New World. Barry Fell and other authors caused a craze in the 1970s when they claimed to have found numerous inscriptions of Ogam, an ancient Irish script, all over the United States. There's a good page on this controversy at the Council for West Virginia Archaeology website. Well worth a look.