What is the longest interstate in the United States?

Interstate 90 runs from Boston, Massachusetts to Seattle, Washington and is 3101 miles long. In addition, I-90 travels through major cities such as Billings, Montana, Chicago, Cleveland and Buffalo,NY. It is the 9th longest Highway in the world. For the most part I-90 parallels US Hwy 20 and passes through 13 states. Even numbered highways indicate an east/west directional path. Odd numbered routes are north/south roadways.

I-95 is 1926 miles

I-80 is 2900 miles

I-10 is 2460 miles