1. Louisiana Became a US Territory: On May 21, 1812, Louisiana officially became a United States territory. This happened as part of the Louisiana Purchase, which saw the U.S. acquire a vast swath of land from France in 1803. Louisiana became the 18th state to join the union on April 30, 1812, just a few weeks before it officially became a territory.

2. First Sugar Refinery in Louisiana: On May 21, 1751, the first sugar refinery in Louisiana was established in New Orleans. This was an important milestone in the state's history, as sugarcane became a major cash crop for Louisiana and the surrounding region. Sugar plantations were instrumental in driving the state's early economic growth.

3. LSU Established: Louisiana State University (LSU) was established on May 21, 1860. The school is located in Baton Rouge and is the flagship institution of the Louisiana State University System. LSU is well known for its strong academics and high-profile athletics programs.

4. Huey P. Long Bridge Opens: The Huey P. Long Bridge in New Orleans opened on May 21, 1935. The bridge spans the Mississippi River and was named after former Louisiana Governor Huey P. Long. It was one of the longest bridges in the world at the time of its opening and played an important role in facilitating commerce and travel in the region.

5. Record Rainfall: On May 21, 1957, New Orleans experienced one of its heaviest rainfall events on record. Over 10 inches of rain fell in a 24-hour period, causing widespread flooding and damage throughout the city. The event is still remembered as one of the most severe weather events in New Orleans' history.