Check out the Students for Martin Luther King, Jr. Day button we found online at LearnCalifornia.org:
This button was worn during the bill signing ceremony of 1981 which created a California state holiday on Dr. King’s birthday, January 15th. Later, in 1983, President Reagan signed a bill creating a federal holiday to honor King, which is now observed on the third Monday each January. But it took 17 more years for the holiday to be observed in all 50 states— Arizona (1992), New Hampshire (1999) and Utah (2000) were the last three states to recognize the holiday.
For more historical buttons check out the Busy Beaver Button Museum at buttonmuseum.org.