1. On May 15, 1869, the territorial legislature of Montana met for the first time in the city of Helena. Montana had been made a territory of the United States just a few months earlier, in March of that same year.

2. In 1918, the deadliest earthquake in Montana history struck the town of Helena on May 15. The quake, which had a magnitude of 6.6, caused extensive damage to buildings in the city and was felt as far away as Spokane, Washington.

3. May 15 is also National Peace Officers Memorial Day, a day set aside to honor and remember law enforcement officers who have lost their lives in the line of duty. In Montana, this day is also observed with a statewide memorial service held in Helena.

4. In 1936, the Montana state legislature designated the Bitterroot flower (Lewisia rediviva) as the state flower. This small, pinkish-white flower is native to the Rocky Mountains and can be found in many parts of Montana. May 15 is recognized as Bitterroot Day in Montana to celebrate this beautiful flower.

5. On May 15, 2007, Helena native Brian Schweitzer was sworn in as the Governor of Montana for his second term. Schweitzer, a Democrat, was known for his populist views and his efforts to expand renewable energy production in the state.