1. On April 20, 1839, the first steamboat arrived in Washington Territory. The Columbia, the first steam-powered vessel to navigate the Columbia River, made its way up to Fort Vancouver in what is now Washington State.

2. In 1853 on April 20, the Territorial Legislature of Washington established the University of Washington. Originally called the Territorial University of Washington, it opened its doors on November 4, 1861, with a class of just 30 students.

3. On April 20, 1910, the city of Seattle was devastated by a massive fire. Known as the "Great Seattle Fire," it destroyed 29 city blocks and caused over $20 million in damages.

4. In 1971 on April 20, the state of Washington became the first in the country to legalize abortion. The landmark Washington State law made abortion legal before the Supreme Court's landmark Roe v. Wade decision in 1973.

5. On April 20, 1999, the deadliest high school shooting in U.S. history occurred at Columbine High School in Colorado. While not directly related to Washington history, the event had a significant impact on the state and the nation, sparking a national conversation about gun violence and school safety.