1. Louisiana Purchase: On June 15, 1804, the United States extended its territory with the Treaty of St. Ildefonso, which transferred the Louisiana Territory from Spain to France. This marked the beginning of negotiations that would lead to the Louisiana Purchase, the historic acquisition of Louisiana by the U.S. in 1803.

2. First Steamship Voyage: On June 15, 1811, the first steamship to navigate the western waters of the United States, the New Orleans, made its maiden voyage from Pittsburgh to New Orleans. This opened up a new era of transportation and trade on the Mississippi and Ohio Rivers.

3. Creole Rebellion: On June 15, 1846, the Creole rebellion took place in New Orleans, where Creole sailors who were en route to Georgia to be sold as slaves revolted and took control of the ship. The incident had international implications because it took place on a British ship, and it raised questions about Britain's involvement in the practice of slavery in America.

4. Huey Long Assassination Attempt: On June 15, 1934, Louisiana Governor Huey P. Long was shot at the State Capitol building in Baton Rouge by Dr. Carl Austin Weiss. Long's injuries proved fatal, and his death led to political turmoil and a power struggle in Louisiana.

5. Hurricane Audrey: On June 15, 1957, Hurricane Audrey made landfall in south Louisiana, causing widespread destruction and killing more than 400 people. The storm was notable for its sudden intensification and the lack of warning given to residents in the affected areas. The devastation prompted changes in hurricane warning systems and evacuation procedures.