1. On May 21, 1900, the Illinois state legislature passed the Sullivan Law, which required premarital examinations for couples seeking marriage licenses as a way to prevent the spread of syphilis. This was one of the earliest laws of its kind in the United States.

2. The first transcontinental airmail service in the United States began on May 21, 1920, when pilot Jack Knight flew from New York to San Francisco with a bag of mail. Illinois was one of the 13 states along the route.

3. May 21, 1930, marked the dedication of the Norris Dam on the Clinch River in Tennessee, which was built in part with funding from the Illinois Valley Authority. The dam provided electricity and flood control for the region.

4. The first McDonald's restaurant opened in Des Plaines, Illinois, on May 21, 1955. The fast food chain, which was founded by Ray Kroc, would go on to become one of the most successful in the world.

5. On May 21, 1979, Illinois Governor James Thompson signed legislation making Illinois the first state to adopt a statewide ban on smoking in public places. The law was controversial at the time but has since been followed by dozens of other states and countries around the world.