March 20 is an important day in Washington state's history with several notable events that happened on this day. Here are five interesting facts about March 20 in Washington history:

1. In 1911, the Washington State Legislature passed a bill granting women the right to vote. This was a significant milestone in the history of the suffragette movement in the United States and Washington state became the fifth state to extend this right to women.

2. In 1948, the Washington State Legislature passed the Industrial Welfare Act, which established the state's minimum wage laws. The law required employers to pay at least 75 cents an hour for all workers in the state, regardless of their occupation or industry.

3. The Seattle World's Fair officially opened on March 20, 1962. The six-month-long exhibition, also known as the Century 21 Exposition, showcased futuristic technologies and ideas and attracted over 10 million visitors from around the world.

4. In 1980, Mount St. Helens, a volcanic peak located in southwestern Washington, experienced a magnitude 4.2 earthquake, signaling the volcano's impending eruption. The eruption occurred two months later, on May 18, and was one of the most destructive volcanic events in U.S. history.

5. On March 20, 2006, the Seattle Seahawks announced that they had acquired running back Shaun Alexander, who would go on to set a team record with 28 touchdowns that season and lead the Seahawks to their first Super Bowl appearance in franchise history.

In summary, March 20 has been significant in Washington state's history with notable achievements in women's suffrage, labor laws, and sports, as well as a devastating natural disaster.