1. On August 20, 1832, the Black Hawk War officially ended with the signing of the Treaty of Fort Armstrong between the United States government and the Sauk and Fox tribes. The war, which lasted from April to August of that year, resulted in the defeat of the Native American tribes and the forced relocation of their people to reservation lands west of the Mississippi River.

2. In 1920, on August 20, the Illinois State Senate ratified the 19th Amendment to the United States Constitution, granting women the right to vote. Illinois was the first state to do so after the amendment was passed by Congress, and its ratification helped to pave the way for the amendment's eventual adoption nationwide.

3. August 20, 1931, marked the dedication of the famous "Million Dollar Quartet" mural in Memphis, Tennessee, which commemorated the impromptu recording session at Sun Studio that brought together Elvis Presley, Jerry Lee Lewis, Carl Perkins, and Johnny Cash. The mural was created by Chicago artist Anthony Guccione and remains a popular tourist attraction to this day.

4. On August 20, 1960, Chicago police arrested 200 people during a protest outside of the Democratic National Convention. The demonstration was organized by members of Students for a Democratic Society and other anti-war activists who were protesting the party's failure to take a firm stance on civil rights and the Vietnam War.

5. In 1980, on August 20, the famous Chicago stalactite cave known as the "old Kentucky cave" was opened to the public. Discovered in 1925 during the construction of an underground freight tunnel, the cave features a unique array of dripstone formations and underground streams, and was a popular tourist attraction for several decades before being closed due to safety concerns in the 21st century.