1. In 1927, the Mississippi River reached its highest recorded level in Louisiana history, flooding over 27,000 square miles of land and displacing over 640,000 people. This event is still known as the Great Flood of 1927 and is considered one of the worst peacetime disasters in American history.

2. On May 18, 1978, the American Federation of Labor and Congress of Industrial Organizations (AFL-CIO) held a rally in Baton Rouge to protest proposed laws that would restrict workers' rights to strike and unionize. Over 20,000 people attended the event, which was one of the largest labor demonstrations in Louisiana history.

3. In 1803, the United States completed its purchase of Louisiana from France, which doubled the size of the country overnight. While the actual transfer of power didn't occur until December of that year, May 18 is considered the anniversary of the Louisiana Purchase.

4. Louisiana State University (LSU) was officially founded on May 18, 1860, as Louisiana State Seminary of Learning and Military Academy. The school was originally established to provide higher education to the state's young men and teach military tactics, but it has since grown into a major research university with over 30,000 students.

5. On May 18, 2015, New Orleans celebrated the 300th anniversary of its founding. The city was founded by the French explorer Jean-Baptiste Le Moyne de Bienville in 1718 and has since become one of the most vibrant and culturally rich cities in the United States. The tricentennial celebration included parades, festivals, and other events throughout the year.