After numerous cost overruns and delays, a 1.8 mi highway tunnel in Seattle, Washington, U.S., opens to traffic, becoming the largest road tunnel in the contiguous United States. It was bored using Bertha, the world's largest tunnel boring machine.
- Washington Post
Bertha, once the world's largest tunnel boring machine, completes its 9,270 ft tunnel under Seattle, Washington, after four years of digging and a lengthy delay near the beginning of the project.
The Space Needle in Seattle unveils the world's first revolving glass floor.
Seattle becomes the first major U.S. city to ban plastic straws and utensils in all bars and restaurants.
Seattle's city council votes 7–2 to repeal a controversial employer head tax, which was approved a month earlier.
Former US District attorney Jenny Durkan is elected mayor of Seattle, becoming the city's first woman mayor since 1926.