what are two groups who discovered america by crossing the atlantic before columbus? (not the vikings)

Long before America was discovered by Columbus, a band of Irish monks led by Saint Brenden visited Americas in sixth century. They traveled on ox-boats and returned after seven years. They reported that they have discovered a land full of vegetation, people believe that the land he mentioned was Newfoundland.

Some scholars say that before Vikings America was visited by Chinese travelers and also by visitors from Ice Age Europe and Africa.

lewis and clark (i think)

the alfred thayer mahan award for literary achievement is awarded each year by the navy league of the united states. the award is named for an american naval historian and theorist, rear admiral alfred thayer mahan, united states navy who, through his writing, provided stimulus and guidance to those who share in the defense of the nation. presented since 1957, "this award for literary achievement is awarded to a u.s. navy officer, u.s. marine corps officer, enlisted service member, or civilian who has made a notable literary contribution that has advanced the knowledge of the importance of sea power in the united states."[1]