1. The Washington Monument officially opened on May 15, 1888. The monument, dedicated to the first President of the United States, stands at 555 feet tall and is the tallest stone structure in the world.

2. On May 15, 1970, anti-war protestors began a five-day occupation of the federal courthouse in downtown Seattle. The protest was in response to the Nixon administration's invasion of Cambodia and escalation of the Vietnam War. The occupation ended peacefully with no arrests or injuries.

3. May 15, 1918, marked the opening of the Ballard Locks in Seattle. The locks allow boats to pass between Lake Union, Lake Washington, and Puget Sound, making it an important transportation hub for the city and a popular tourist attraction.

4. In 1980, on May 18, Mount St. Helens erupted in what is considered one of the most destructive volcanic events in U.S. history. The volcano, located in southwestern Washington, spewed ash and debris over 230 square miles, causing widespread destruction and killing 57 people.

5. May 15, 1961, saw the founding of the Seattle Children's Theater, which has since become one of the largest and most respected children's theaters in the country. The theater produces a wide variety of plays and musicals for both children and adults, and has received numerous awards for its work.