Is route 80 the longest route in the usa?

Interstate 90 is 3,112 miles long. and is the longest Interstate in the US...

Interstate 90 (abbreviated I-90) is the longest interstate highway in the United States at nearly 3,112 miles It is the northernmost east-to-west, coast-to-coast interstate. Its western terminus is in Seattle, Washington at 4th Avenue S. next to Qwest Field, and its eastern terminus is in Boston, Massachusetts at Route 1A near Logan International Airport. It crosses the Continental Divide just east of Butte, Montana.

Interstate 80 was originally only 2,909 miles, making it the 2nd longest road in the United States, from Oakland, CA to NYC, NY......BUT the entire segment west of Dallas, Texas has been decommissioned in favor of various Interstate highways and state highways. The current length of I-80 is only 1,032 miles

Routh 66 would have been longer than Route 80, but parts of it's roads have fallen into dis-use.

U.S. Route 66, (also known as Route 66, The Main Street of America, The Mother Road and the Will Rogers Highway "was" a highway in the U.S. Highway system. One of the original federal routes, US 66 was established on November 11, 1926, though signs did not go up until the following year It originally ran from Chicago, Illinois through Missouri, Kansas, Oklahoma, Texas, New Mexico, Arizona and California before ending at Los Angeles for a total of 2,448 miles

en.wikipedia.org/wiki/Interstate_90

en.wikipedia.org/wiki/U.S._Route_80