September 20 has played a prominent role in Washington state's history. Here are five interesting facts about this day:

1. In 1908, Mount Rainier National Park was established, becoming the fifth national park in the United States. The park is a popular destination for hiking, skiing, and mountaineering, and is famous for its beautiful vistas of Washington's tallest peak, Mount Rainier.

2. On September 20, 1977, the St. Helens National Volcanic Monument was created following the devastating eruption of Mount St. Helens earlier that year. The monument serves as a reminder of the power of nature and the importance of conservation efforts.

3. In 1983, the Seattle Mariners, the city's Major League Baseball team, played their final game at the Kingdome before moving to their current home, T-Mobile Park. The Kingdome was the first domed stadium in the world with a roof made of concrete and stood for over 24 years until its implosion in 2000.

4. Seattle's first-ever rainfall was recorded on September 20, 1851. As a result, the city is known for its rainy weather and is sometimes referred to as the "rainy city."

5. In 2000, Paul Allen, the co-founder of Microsoft, opened the Experience Music Project (now known as MoPOP) in Seattle. The museum celebrates and showcases popular culture, with exhibits on music, science fiction, and video games. It also houses the world's largest collection of Jimi Hendrix memorabilia.