Casimir Pulaski Day is a holiday observed in Illinois on the first Monday of every March to commemorate Casimir Pulaski (March 4, 1745[1] – October 11, 1779), a Revolutionary War cavalry officer born in Poland as Kazimierz Pułaski. He is known for his contributions to the U.S. military in the American Revolution by training its soldiers and cavalry.
The day is celebrated mainly in areas that have large Polish populations, such as Chicago. The focus of official commemorations of Casimir Pulaski Day in Chicago are at the Polish Museum of America where various city and state officials congregate to pay tribute to Chicago's Polish Community.
This is a separate holiday from the federal holiday, General Pulaski Memorial Day, which commemorates Pulaski's death from wounds suffered at the Siege of Savannah on October 9, 1779.
Illinois enacted a law on June 20, 1977, to celebrate the birthday of Casimir Pulaski and held the first official Pulaski Day celebrations in 1978. The bill was introduced by State Senator Leroy W. Lemke, a Democrat from Chicago. Chicago Public Schools, Cook County government offices, and the Chicago Public Library close on this holiday.
http://en.wikipedia.org/wiki/Casimir_Pulaski_Day