1. On October 20, 1864, the Battle of Decatur took place in Decatur, Tennessee during the American Civil War. Union soldiers successfully defended the city against Confederate forces.

2. In 1953, the first atomic reactor in the South was dedicated in Oak Ridge, Tennessee on October 20. The reactor was used for nuclear research and development.

3. On October 20, 1803, the Treaty of Tellico was signed between the United States and the Cherokee Nation, ceding a large portion of Cherokee land to the U.S. government.

4. Knoxville, Tennessee's first African American mayor, Daniel Brown, was inaugurated on October 20, 1976. Brown was a civil rights activist and served as mayor for two terms.

5. On October 20, 1923, the Great Smoky Mountains National Park was officially dedicated in Gatlinburg, Tennessee. The park spans over 500,000 acres and is the most visited national park in the United States.