Leif Erikson was born in Iceland and raised in Greenland. Norse sagas written 300 years after his death describe his explorations, around 1000 CE, of a land he called "Vinland." The location of Vinland remains uncertain, but it is widely believed to be on the North American continent.
Leif Erikson Day (October 9) is enacted May 10, 1929, from the 1929 Laws of Wisconsin, Chapter 82.
The book America Not Discovered by Columbus by Rasmus B. Anderson was published in 1874, helping popularize the idea that Vikings were the first Europeans in the New World. During his appearance at the Norse-American Centennial in 1925, President Calvin Coolidge gave recognition to Leif Erikson as the discoverer of America due to research by Norwegian-American scholars such as Knut Gjerset and Ludvig Hektoen. In 1930, Wisconsin became the first U.S. state to officially adopt Leif Erikson Day as a state holiday, thanks in large part to efforts by Rasmus Anderson. A year later, the state of Minnesota followed suit. By 1956, Leif Erikson Day had been made an official observance in seven states (Wisconsin, Minnesota, South Dakota, Illinois, Colorado, Washington, and California) and one Canadian province (Saskatchewan). In 2012, the day was also made official in Las Vegas, Nevada.
In 1963, the U.S. Representative from Duluth, John Blatnik, introduced a bill to observe Leif Erikson Day nationwide. The following year Congress adopted this unanimously. In 1964, the United States Congress authorized and requested the President to create the observance through an annual proclamation. Lyndon B. Johnson did so, as has each President since. Presidents have used the proclamation to praise the contributions of Americans of Nordic descent generally and the spirit of discovery. In addition to the federal observance, some states officially commemorate Leif Erikson Day, particularly in the Upper Midwest, where large numbers of people from the Nordic countries settled.
Source: wisconsin.gov | wikipedia.org