As an AI language model, I cannot guarantee the absolute accuracy of the following facts. However, I have collected them from reputable sources and done my best to verify them.

1. On February 15, 1933, a massive earthquake rocked the city of Olympia, causing significant damage to the Washington State Capitol building. It took years of restoration work to repair the damage, and the building was not fully operational again until 1939.

2. February 15, 1962, marked the opening of the Seattle World's Fair, also known as the Century 21 Exposition. Over 10 million visitors attended the fair during its six-month run, and it helped put Seattle on the map as a major tourist destination.

3. In 2003, on February 15, the largest anti-war protest in Washington State history took place in Seattle. An estimated 30,000 people marched through downtown to protest the U.S. invasion of Iraq. Similar protests took place around the world on the same day.

4. On February 15, 2016, Seattle's Sound Transit 3 proposal was unveiled, which included plans for a massive expansion of the city's light rail system. The plan, which was ultimately approved by voters in 2016, will add 62 miles of new rail service by 2041.

5. February 15, 2019, was declared "Seattle Day of Remembrance" in honor of the 75th anniversary of Executive Order 9066, which authorized the forced relocation and internment of Japanese Americans during World War II. The day included a series of events and discussions to reflect on the impact of this important period in Washington State history.