1. On April 27, 1907, Seattle's first all-concrete building, the Alaska Building, was dedicated. It was named after the nearby Alaska-Yukon-Pacific Exposition, which celebrated the 10th anniversary of the Klondike Gold Rush.

2. In 1945, the United States Navy used the Puget Sound Naval Shipyard in Bremerton to repair and maintain warships used in World War II. On April 27 of that year, the submarine USS Tinosa was launched from the shipyard after undergoing extensive repair and modernization.

3. On April 27, 1975, the Seattle Mariners played their first home game in franchise history at the Kingdome. They faced off against the California Angels and won 7-0, with starting pitcher Diego Segui throwing a shutout game.

4. In 1984, Washington became the first state in the United States to ban discrimination based on sexual orientation by enacting the Washington Law Against Discrimination. The law was signed by Governor John Spellman on April 27 and remains in effect today.

5. On April 27, 2016, Mount St. Helens, a volcano located in southwestern Washington, experienced a small earthquake swarm. The largest of these earthquakes measured a magnitude of 2.4 and was the largest seismic activity recorded at the volcano since November 2014.