Wisconsin’s 21 special observance days are part of state statutes governing general school operations (Wis. Stat. sec. 118.02). Federal law has moved the celebration of many legal holidays to Monday, however, state law recommends that each Wisconsin Special Observance Day be held on the day itself. When an observance day falls on a Saturday or Sunday, it should be observed on the preceding Friday or the following Monday. Dr. Martin Luther King Jr. Day in Wisconsin is an observance on January 15.
Dr. Martin Luther King Jr. was a leader of the American civil rights movement in the 1950s and 1960s. Before his assassination in 1968, he received the Nobel Peace Prize for his efforts to use nonviolent resistance to achieve equality for African Americans. His efforts contributed to passage of the Civil Rights Act of 1964 and the Voting Rights Act of 1965.
(Wisconsin Public School Observance Days. Dr. Martin Luther King Jr. Day Enacted May 3, 1976, from the 1975 Laws of Wisconsin, Chapter 219.)
Source: wisconsin.gov