1. On December 18, 1817, Mississippi was officially admitted as the 20th state of the United States.

2. In 1865, less than a year after the Civil War ended, the 13th Amendment to the US Constitution was ratified by Mississippi's legislature, abolishing slavery in the state.

3. On this day in 1948, the Mississippi State Sovereignty Commission was established as a reaction to the US Supreme Court's decision in Brown v. Board of Education, which declared segregation in public schools unconstitutional. The commission worked to maintain segregation and suppress civil rights activism in the state for over two decades.

4. The Mississippi Freedom Democratic Party (MFDP) was formed on December 18, 1964. The group, which was made up primarily of African American activists, sought to challenge the all-white Democratic Party's dominance in state politics and push for voting rights and other civil rights reforms.

5. In 1987, a deadly tornado outbreak struck Mississippi on December 18, killing at least 12 people and causing widespread damage. The tornadoes were part of a larger outbreak that affected several states in the southeastern US.