The Medieval Warming Period may have helped the Norse discover North America by reducing North Atlantic ice, making the crossing easier.
They didn't necessarily get far into North America, but on the extreme northern tip of the island of Newfoundland in Canada, there is an archaeological site at L'Anse aux Meadows (Meadows Cove). Begun in 1960, the remains of three structures were found whose timbers via tree-ring dating showed they were cut down about 1021CE. (Model of the village to the left.)One of the structures contained iron slag, showing that it was a smithy. Stone weights found in one building are consistent with the type used in looms. These suggest the place was not just a seasonal hunting camp, but intended to be a long-term settlement.
One question that remains about this site is: is it the Vinland mentioned in literature? In 1073, a German cleric writes
He [the Danish king, Sven Estridsson] also told me of another island discovered by many in that ocean. It is called Vinland because vines grow there on their own accord, producing the most excellent wine. Moreover, that unsown crops abound there, we have ascertained not from fabulous conjecture but from the reliable reports of the Danes.
Vinland is mentioned in two Icelandic sagas: the Saga of Erik the Red and the Saga of the Greenlanders. They discuss the discovery by Norse Greenlanders of land to the west of Greenland that they call Vinland. Although there is no direct evidence to support the theory, many are content to link the settlement at L'Anse aux Meadows with Vinland. Why didn't the settlement grow and continue? The sagas suggest that internal conflict among the Norse as well as conflict with the peoples native to Vinland caused the failure of the settlement.
I'll talk a little more about the Norse encounter with the natives tomorrow.