1. The Louisiana Purchase Treaty was signed on May 15, 1803, which effectively doubled the size of the United States. This historic agreement gave the U.S. control over the Mississippi River and the port city of New Orleans, among other territories.

2. On May 15, 1862, Union forces captured New Orleans during the Civil War. This key victory allowed the Union to control the important port city and provide a base for further operations in the deep South.

3. The first jazz recording was made on May 15, 1917, in New Orleans by the Original Dixieland Jazz Band. This groundbreaking recording helped popularize jazz music throughout the country and around the world.

4. On May 15, 1957, the United States Supreme Court ruled in the case of Hayes v. Louisiana that African Americans could not be excluded from serving on juries based on their race. This landmark decision helped pave the way for greater civil rights in Louisiana and across the nation.

5. Finally, on May 15, 1970, the Louisiana Superdome officially opened in New Orleans. This massive stadium, which has since been renamed the Mercedes-Benz Superdome, is one of the largest sports and entertainment venues in the world and has hosted numerous high-profile events, including seven Super Bowls.