South Dakota Codified Laws
Chapter 05 - Time And Dates
Section 1-5-1.3 - South Dakota Statehood Day established.

1-5-1.3. South Dakota Statehood Day established.
The second day of November, to be known as South Dakota Statehood Day, shall be observed in this state as a working holiday. South Dakota Statehood Day is dedicated to the remembrance of the anniversary of South Dakota's admittance into the union on November 2, 1889. This day will be to reflect on the history and the heritage of the state.

Source: SL 2001, ch 6, ยง1.