Washington State Route 90, commonly known as I-90, is a major east-west interstate highway in the United States. It stretches approximately 3,020 miles from Seattle, Washington to Boston, Massachusetts, making it one of the longest interstate routes in the country. In Washington, I-90 runs through diverse landscapes, including mountains, forests, and urban areas. In Washington State, I-90 serves as a vital transportation corridor, connecting major cities like Spokane and Seattle. The highway features several important structures, including the Lake Washington Floating Bridge, which is one of the longest floating bridges in the world. I-90 plays a crucial role in facilitating commerce and travel across the state.