The longest road in the United States was once the second longest: U.S. 20 from Boston, Massachusetts to Newport, Oregon, passing through Wyoming along the way.

U.S. Route 20 or U.S. Highway 20 (US 20) stretches east to west from the Pacific Northwest all the way to New England. It spans 3,365 miles and is the longest road in the United States

Moving West to East - US 20 in Wyoming begins at the eastern entrance to Yellowstone National Park and joins with US 14 and US 16.

Together, the routes run to Greybull, where US 14 continues east and US 16/US 20 turns south; at Worland, US 16 turns east. US 20 runs south and passes through Wind River Canyon south of Thermopolis.

US 20 then turns to join US 26 in Shoshoni, where it turns east, and continues on to Casper. From Casper those highways parallel I-25 and US 87.

They then join together at a point southeast of Glenrock. These four routes continue to Orin, where US 20 separates and turns east from I-25, at the western end of US 18.

Then it's on to Lusk, where US 18 turns north and US 20 continues east into Nebraska.

The longest straight road in the United States, in case  you were wondering, is Highway 412 beginning in Oklahoma from Hardesty to just east of Slapout for 65.5 miles. You can look at Google Earth and see that the road is perfectly straight all that way.

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