1. Missouri becomes the 24th state: On November 15, 1820, Missouri officially became the 24th state to be admitted into the Union. Its entry into the Union was significant as it was the first state to be carved out of the Louisiana Purchase, which was acquired from France in 1803.

2. St. Louis Arch completed: On November 15, 1965, the final section of the Gateway Arch in St. Louis was put into place, completing the iconic monument. The arch rises 630 feet above the city and is the tallest man-made monument in the United States.

3. Mark Twain is born: On November 15, 1835, Samuel Clemens, better known by his pen name Mark Twain, was born in the town of Florida, Missouri. Twain became one of America's greatest and most beloved writers, famous for his humorous, witty, and insightful works such as The Adventures of Tom Sawyer and Adventures of Huckleberry Finn.

4. Missouri Compromise is proposed: On November 15, 1818, Missouri Congressman James Tallmadge proposed what became known as the Tallmadge Amendment to the Missouri Enabling Act. The amendment sought to prohibit the expansion of slavery into Missouri, and sparked fierce debate over the issue of slavery in the United States.

5. Truman Library opens: On November 15, 1957, the Harry S. Truman Presidential Library and Museum opened its doors to the public in Independence, Missouri. The library houses the official papers and documents of the 33rd President of the United States, as well as exhibits detailing Truman's life and presidency.