1. Lincoln-Douglas Debate: On August 21, 1858, Abraham Lincoln and Stephen A. Douglas held the fifth of their seven debates in Ottawa, Illinois. These debates were a pivotal moment in American politics as they discussed issues such as slavery, states' rights, and popular sovereignty.

2. Great Fire of 1918: On August 21, 1918, a fire broke out in the Illinois city of Urbana. The fire burned through the business district, destroying over 100 buildings and causing $1.5 million in damages.

3. Birth of William Brink: Born on August 21, 1904, William Brink was a journalist and activist who played a major role in the labor movement in Illinois. Brink was a co-founder of the Industrial Workers of the World (IWW) and was known for his fiery speeches and dedication to workers' rights.

4. Chicago Race Riot: On August 21, 1966, a riot broke out in Chicago's West Side neighborhood. The riot was sparked by tensions between African Americans and the city's police department and lasted for several days. The riot resulted in over 40 injuries and millions of dollars in property damage.

5. Lincoln-Swayze Duel: On August 21, 1842, Abraham Lincoln participated in a duel with James Shields, the State Auditor of Illinois. The two men had a long-standing feud, and after Shields challenged Lincoln to a duel, the two met on a sandbar in Missouri. Fortunately, the duel was averted when Lincoln's second suggested that they resolve the conflict peacefully.