What is the longest Interstate Highway in the United States?

Interstate 90 (I-90) is an east–west transcontinental freeway and the longest Interstate Highway in the United States at 3,021 miles (4,862 km). It begins in Seattle, Washington, and travels through the Pacific Northwest, Mountain West, Great Plains, Midwest, and the Northeast, ending in Boston, Massachusetts. The highway serves 13 states and has 15 auxiliary routes, primarily in major cities such as Chicago, Cleveland, Buffalo, and Rochester. The freeway was established by the Federal-Aid Highway Act of 1956, replacing a series of existing U.S. highways that had been preceded by local roads and auto trails established in the early 20th century. I-90 was numbered in 1957, reflecting its status as the northernmost transcontinental route of the system.

Source: Wikipedia