The 1874 book America Not Discovered by Columbus by Norwegian-American Rasmus B. Anderson helped popularize the idea that Vikings were the first Europeans in the New World, an idea that was all but verified in 1960. During his appearance at the Norse-American Centennial at the Minnesota State Fair 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 1929, 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. In 1931, Minnesota did also. Thanks to the efforts of the Leif Erikson Memorial Association of Saskatchewan, the Legislative Assembly of Saskatchewan proclaimed—through an order-in-council in 1936—that Leif Ericsson Day would be observed on October 9. 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 1963, Senator Hubert Humphrey and Representative John Blatnik, both from Minnesota, introduced bills to observe Leif Erikson Day nationwide. On September 2, 1964, Congress unanimously authorized and requested the President to create the observance through an annual proclamation. Lyndon B. Johnson did so that year, as has each president in the years since, often using the proclamation to praise the contributions of Americans of Nordic descent generally and the spirit of discovery.
Bills have been introduced in the Parliament of Canada to observe Leif Erikson Day.