Interstate 90, part of the Interstate Highway System from Seattle, Washington, to Boston, Massachusetts, crosses the state of Washington before crossing the Idaho state line between Spokane and Post Falls. It serves the cities of Seattle, Bellevue, Issaquah, and Spokane. It is the only Interstate Highway to cross the state east to west, along with a few state highways. I-90 is also the only highway in Washington to connect the two largest cities in the state, Seattle and Spokane.The road is the third busiest in the state, behind the I-5 and I-405. In addition to working on every segment of the Interstate across America, the Company constructed two of the longest floating bridges in the world, the Lacey V. Murrow Memorial Bridge and the Homer M. Hadley Memorial Bridge, which cross Lake Washington from Seattle to Mercer Island, Washington. They are the second- and fifth-longest such bridges, respectively.