1. Abraham Lincoln's Birthday: May 30th is the birthday of former US President Abraham Lincoln who was born in Hodgenville, Kentucky in 1809. Although he was not born in Illinois, he spent much of his adult life in the state and is well-known for his work as a lawyer and politician there.

2. First Memorial Day: May 30th is recognized as the original Memorial Day. In 1868, General John A. Logan, a native of Illinois, officially proclaimed the day for decorating the graves of soldiers who died fighting for the Union during the American Civil War. The first Memorial Day was celebrated at Arlington National Cemetery.

3. Chicago’s First Skyscraper: On May 30th, 1884, the Home Insurance Building was completed in Chicago, Illinois, becoming the world's first skyscraper. It stood 10 stories high and was the first building to use a steel skeleton rather than load-bearing walls. This design paved the way for taller buildings in the future.

4. USS Illinois: The USS Illinois was a battleship constructed in 1898, which served the United States Navy until the end of World War I. It was the second ship to be named after the state of Illinois, and was launched on May 30th, 1899. The ship weighed over 16,000 tons and was equipped with four 13-inch guns and twenty 6-inch guns.

5. Mayor Harold Washington: Harold Washington was sworn in as the first African American Mayor of Chicago, Illinois, on May 30th, 1983. He was known for his efforts to reform the city's political system and bring about racial equality. Washington served as Mayor until his death in 1987.