1. On April 12, 1945, President Franklin D. Roosevelt died of a massive stroke at his vacation home in Warm Springs, Georgia. Roosevelt, who served as president from 1933 until his death, is remembered as one of the most influential presidents in U.S. history for his leadership during World War II and his implementation of the New Deal which greatly improved the nation's economy.

2. In 1861, the American Civil War began when Confederate forces attacked Fort Sumter in South Carolina. Illinois played a major role in the war effort and contributed over 250,000 soldiers to the Union army – more than any other northern state. Many of the state's soldiers fought in significant battles such as the Battle of Gettysburg and the Battle of Shiloh.

3. The city of Chicago was incorporated on April 12, 1837. Chicago is now the third-largest city in the United States and one of the most culturally diverse cities in the world. It is known for its architecture, food, and sports teams and is a major transportation and economic hub.

4. Famous American blues musician, singer, and songwriter Muddy Waters was born on April 12, 1913, in Rolling Fork, Mississippi. Waters moved to Chicago in the 1940s where he developed his signature sound and became known as the "father of modern Chicago blues". He was inducted into the Blues Hall of Fame in 1980 and the Rock and Roll Hall of Fame in 1987.

5. University of Illinois mathematician Grace Murray Hopper completed the first successful run of the Mark I computer on April 12, 1945. The Mark I was one of the first large-scale automatic digital computers and was used by the United States Navy during World War II. Hopper later went on to develop the first compiler which allowed programmers to write code in English rather than numerical code.