1. In 1920, the United States Post Office Department issued a commemorative stamp marking the 300th anniversary of the landing of the Pilgrims at Plymouth Rock, Massachusetts. This was significant for Washington residents, as many of the first settlers in the state were also of Pilgrim descent.

2. On May 16, 1933, the Washington State Department of Agriculture introduced a new variety of apple called the "Golden Delicious," which quickly became one of the most popular apple varieties in the world.

3. In 1951, Seattle's historic Smith Tower was sold for $1.8 million, making it the most expensive real estate transaction in the city's history at the time. The tower still stands as a National Historic Landmark and popular tourist destination.

4. On May 16, 1972, the Washington State Capitol building suffered a major fire that destroyed much of the building's interior. The building was eventually restored and reopened in 1989.

5. In 2004, the first same-sex marriage ceremony in the United States was performed in Washington State. This historic event paved the way for other states to legalize same-sex marriage in the years that followed.