1. On December 15, 1824, the Illinois General Assembly passed the Internal Improvement Act, which authorized the state to undertake a comprehensive program of public works. The act led to the construction of a vast network of roads, bridges, canals, and railroads, which helped to stimulate economic growth and development throughout the state.

2. In 1863, Abraham Lincoln issued his famous Proclamation of Amnesty and Reconstruction, which offered a full pardon to most Confederate sympathizers who would take an oath of loyalty to the Union. The proclamation was issued on December 8, but it was on December 15 that it was officially published in the state of Illinois.

3. One of the most famous tragedies in Illinois history occurred on December 15, 1910, when the Cherry Mine in Cherry, Illinois, exploded, killing 259 miners. The disaster was one of the deadliest in American mining history and led to significant reforms in workplace safety regulations.

4. On December 15, 1939, the Illinois National Guard mobilized for duty in World War II. Over 300,000 men and women from Illinois served in the armed forces during the war, with many receiving honors for bravery and heroism.

5. In 2008, Governor Rod Blagojevich was impeached on charges of corruption and abuse of power. The impeachment vote took place on December 15, and Blagojevich was subsequently removed from office by the Illinois Senate. He was later sentenced to 14 years in federal prison for a variety of crimes related to his time as governor.