In 574 AD Saint Brendan started colonies in three places while looking for Paradise: Iceland, Greenland, and New Clonfert. Saint Brendan had a lasting effect on the world as he jump-started Norse colonization helped them survive. He also brought together the Celtic tribes to form the Celtic Union. He even had the 2 new continents named after him: North Brendania and South Brendania.
Iceland was the first spot colonized by the Celtics. When St. Brendan left on his trip this was the first place he stopped at. Brendan found the land good enough for some farming and also had a lot of lumber. Brendan sent people back to Ireland talking about his discoveries there. The Celtics were amazed and had more people go there. The people found Brendan was right. Settlements were started on the southern part of the island. Many farms appeared and sent a steady supply of food back to Ireland. As years went on more people came to Iceland. St. Brendan came here numerous times as he started settlements here. The settlers erected a statue of St. Bredan in honor of him. Iceland became the main spot for people who wanted to go west to Greenland or North Brendania (OTL North America).
Following Iceland St. Brendan went to Greenland. While staying their he and his followers started another settlement. The new settlement traded with the local Natives. The settlers learned things about Greenland from the Natives.