21 of the longest highways in the US

August 2024 · 5 minute read

Although it was officially decommissioned in 1985, US Route 66 still symbolizes the spirit of America — and the allure of the American road trip.

Thankfully, between the Interstate Highway System and the United States Numbered Highway System, there's no shortage of meandering routes to choose from when planning your next adventure. 

From Interstate 25, which traverses the Rocky Mountains as it connects New Mexico and Wyoming, to US Route 20, which spans from Boston, Massachusetts, to Newport, Oregon, here are 21 of America's longest highways. 

I-25: 1,061.67 miles

Signs for Interstate 25 near Truth or Consequences, New Mexico. CGP Grey/Wikimedia Commons

Traversing the Front Range of the Rocky Mountains, Interstate 25 goes from Las Cruces, New Mexico, to Buffalo, Wyoming.

I-5: 1,381.29 miles

A sign for Interstate 5 in Washington State. Airtuna08/Wikimedia Commons

Starting in San Ysidro, a district of San Diego, California, north of the US-Mexico border, Interstate 5 travels up the West Coast to Blaine, Washington — a city whose northern boundary borders Canada.

I-15: 1,433.52 miles

Signs for Interstate 15 in Utah. Garrett/Flickr

Interstate 15 originates in California in San Diego's Mission Valley. Its northern terminus is at the US-Canada border in Sweetgrass, Montana.

I-20: 1,539.38 miles

A sign for Interstate 20 in Mississippi. Ken Lund/Wikimedia Commons

Interstate 20 begins near Kent, Texas, and terminates in Florence, South Carolina.

I-35: 1,568.38 miles

In Minnesota, Interstate 35 splits into I-35W and I-35E. Doug Kerr/Wikimedia Commons

Interstate 35 will take you from Texas — where the highway begins in Laredo — to Minnesota, where it splits into I-35W and I-35E to serve the Twin Cities. 

I-94: 1,585.20 miles

Signs for Interstate 94 in Chicago, Illinois. Tim Boyle/Getty Images

With a western terminus in Billings, Montana, Interstate 90 ends in Port Huron, Michigan. 

I-75: 1,786.47 miles

A sign for Interstate 75 in front of the Sault Ste. Marie International Bridge, which connects Michigan and Canada. Kate Ter Haar/Flickr

Interstate 75 begins in Hialeah, Florida, northwest of Miami. Its northern terminus is located in Sault Ste. Marie, Michigan, on the US-Canada border.  

I-95: 1,919.31 miles

A sign for Interstate 95 in New York. William F. Yurasko/Flickr

Beginning in Miami, Florida, and concluding in Houlton, Maine, I-95 has the distinction of traversing more states than any other Interstate Highway: it passes through a total of 16 states. 

US-52: 2,072 miles

A sign for US Route 52 in West Virginia. Famartin/Wikimedia Commons

On US Route 52, you can travel from Charleston, South Carolina, to the US-Canada border in Portal, North Dakota.

I-70: 2,150.57 miles

A sign for Interstate 70 in Beaver, Utah. Garrett/Flickr

Starting in Cover Fort, Utah, Interstate 70 ends in Baltimore, Maryland.

US-64: 2,326 miles

A sign for US Route 64 in Raleigh, North Carolina. Washuotaku/Wikimedia Commons

US Route 64 connects Teec Nos Pos, Arizona, part of the Navajo Nation, and Whalebone Junction, an area of North Carolina's Outer Banks

I-10: 2,460.34 miles

A sign for Interstate 10 at the McClure Tunnel in Santa Monica, California. steve lyon/Wikimedia Commons

Interstate 10 begins in Los Angeles, California, and extends to Jacksonville, Florida.

I-40: 2,556.61 miles

A sign for Interstate 40 in Knoxville, Tennessee. JJBers/Flickr

Interstate 40 begins in Barstow, California, and ends in Wilmington, North Carolina.

US-1: 2,593 miles

The southernmost point of US Route 1 in Key West, Florida. Anita Walz/Wikimedia Commons

US Route 1, which connects Fort Kent, Maine, and Key West, Florida, originally stopped at Miami. It was extended after the Sunshine State improved the Overseas Highway in the 1930s.

US-2: 2,643 miles

A sign for US Route 2 in Maine. Doug Kerr/Wikimedia Commons

US Route 2 will take you from Houlton, Maine, to Everett, Washington. 

I-80: 2,899.59 miles

A sign for Interstate 80 in Utah. Garrett/Flickr

Interstate 80 connects San Francisco, California, and Teaneck, New Jersey. The highest point of this highway is in Wyoming at Sherman Hill Summit. 

US-50: 3,007 miles

A sign designating US Route 50 as "The Loneliest Road in America." Jack Edge/Wikimedia Commons

Bridging Ocean City, Maryland, and Sacramento, California, US Route 50 is famous for a segment that has been nicknamed the "Loneliest Road in America." The lonesome stretch spans 287 miles through Nevada. (It's a quiet corridor in comparison to I-80, which lies about 100 miles to the north.) 

I-90: 3,020.44 miles

Signs for Interstate 90 on the Massachusetts Turnpike. JJBers/Flickr

Interstate 90, America's longest Interstate Highway, spans from Boston, Massachusetts, to Seattle, Washington.

US-30: 3,073 miles

A sign for US Route 30 in Pennsylvania. Doug Kerr/Wikimedia Commons

US Route 30, America's third-longest highway, travels from the Pacific Ocean in Astoria, Oregon, to the Atlantic Ocean in Atlantic City, New Jersey. 

US-6: 3,227 miles

A sign for US Route 6 in Provincetown, Massachusetts. Jason Mandly/Wikimedia Commons

Also called the "Grand Army of the Republic Highway" — a title that pays homage to the Union forces of the Civil War — US Route 6 spans from Provincetown, Massachusetts, to Bishop, California. 

Sal Paradise, the protagonist of Jack Kerouac's  novel "On the Road," famously eschews this route

US-20: 3,365 miles

A sign for US 20 in Boston, Massachusetts. MassDOT/Wikimedia Commons

US Route 20, part of the US Numbered Highway System, is the longest road in America. Connecting Boston, Massachusetts, and Newport, Oregon, it will take you past points of interest ranging from Cedar Point, an amusement park in Ohio known for its thrilling roller coasters, to odd roadside attractions like Nebraska's Carhenge. 

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