Written by Katrina
Modified & Updated: 01 Oct 2024
Reviewed by Sherman Smith
If you’re a fan of road trips, you’ve probably passed through different highways of different lengths. Sometimes, traveling by car can take just a few hours, while other times, it can take up a whole day. While driving down the highway waiting for traffic to move, you’ve probably wondered to yourself, “what is the longest highway in the United States?”
Whether you’re going on a road trip or simply curious, this guide got you covered! Sit back, put your seatbelt on, and learn all about interstate and U.S. highways while we answer the question, “what is the longest highway in the U.S.?”
What is a highway?
Before we can answer the question, “what is the longest highway in the United States?”, it’s important to first understand what a highway actually is.
It might seem obvious, but people often use “highway” and “freeway” interchangeably. While the two are certainly related, they are not the same thing. A highway is the main road that connects towns, cities, and even states.
Meanwhile, a freeway is also a main road that cars can only access through ramps. The ramps separate freeways from other roads and traffic, which allows vehicles to move faster on freeways. Because of this, a freeway is also called an “express highway” or a “controlled-access highway”.
To put it simply, all freeways are highways, but not all highways are freeways.
How are highways named?
If you travel regularly by car, then you’ve probably already noticed how highways have numbers in their names. Contrary to popular belief, these numbers aren’t randomly assigned. These numbers actually have specific meanings.
The names of interstate highways have the format of Interstate X.
Interstate highways refer to highways that cross state boundaries to connect all 48 U.S. states. These highways belong to the Interstate Highway System. Its name is a combination of the letter “I” and one to three-digit numbers.
Highways with one or two digits in their names are primary interstate highways. Meanwhile, those with three digits in their names are auxiliary interstate highways. Interstate highways with odd numbers connect south to north, while those with even numbers connect west to east.
Meanwhile, the names of U.S. highways have the format of U.S. Highway nn or U.S. Route nn.
U.S. highways, or U.S. routes, belong to the United States Numbered Highway System. Like interstate highways, U.S. highways connect different states. However, most motorists use U.S. highways to travel from one local or regional destination to another.
A U.S. route with even numbers is usually east-to-west roads, while those with odd numbers are usually north-to-south highways. However, U.S. highways don’t have to strictly follow these rules, so there are some exceptions. Because of this, it’s best to have a road map with you when traveling on U.S. highways.
With a better understanding of highway names, it’s time to figure out what the longest highway in the United States is.
What is the longest highway in the United States?
U.S. Route 12 – 2,484 miles
Running for almost 2,500 miles, U.S. Route 12, or simply U.S. 12, is one of the longest highways in the United States. It is an east-west U.S. highway that connects several major cities from Washington to Michigan.
This highway was first opened to the public in 1926. Back then, U.S. 12 only ran from Washington to Montana. Over the years, the highway grew longer and longer until it extended to Downtown Detroit in Michigan. Today, this route also includes Idaho, North Dakota, South Dakota, Minnesota, Wisconsin, Illinois, and Indiana.
However, Interstate 90 and Interstate 94 both supersede U.S. 12 when it comes to traveling between states. However, U.S. 12 continues to be an important route for many motorists who need to travel between local and regional destinations.
Interstate 40 – 2,556 miles
With a length of over 2,500 miles, Interstate 40 is a strong contender. In fact, Interstate 40 is actually the third-longest interstate highway in the United States.
Interstate 40, or simply I-40, is a major east-west highway that passes from North Carolway to California. In between these states, I-40 also passes through Arizona, New Mexico, Texas, Oklahoma, Arkansas, and Tennessee.
This highway first opened in 1952 as a short freeway in Tennessee. Like U.S. 12, I-40 underwent several extensions. Its final extension connected Wilmington to Raleigh, and it finally opened in 1990.
U.S. Route 2 – 2,571 miles
U.S. Route 2, also known as U.S. Highway 2 or U.S. 2, is an east-west highway with an impressive length of 2,575 miles. While it isn’t the answer to the question, “what is the longest highway in the United States?”, it is an important route in the U.S. Highway System.
U.S. 2 has two segments: the eastern segment and the western segment. While newer interstate highways separate most highways, U.S. 2 is segmented by design.
The western segment runs from Everett, Washingway to St. Ignace, Michigan. Other states along the way include Idaho, Montana, North Dakota, Minnesota, and Wisconsin. Meanwhile, the eastern segment runs from Rouses Point, New York to Houlton, Maine. In between, U.S. 2 also connects Vermont and New Hampshire.
U.S. Route 60 – 2,655 miles
Running for over 2,600 miles, U.S. Route 60 is one of the longest highways in the United States. U.S. Route 60, or simply U.S. 60, runs from Arizona to Virginia. If you’re traveling to New Mexico, Texas, Oklahoma, Missouri, Illinois, Kentucky, or West Virginia, you can also take this route.
After the highway first opened in 1926, U.S. 60 ran from Virginia to Missouri. Soon, construction opened once more to extend the route to Los Angeles, California. In the 1950s, however, interstate highways bypassed U.S. 60. By 1972, I-10 had mostly replaced U.S.60, resulting in California decommissioning the old highway.
Interstate 80 – 2,900 miles
While it isn’t the longest highway in the United States, Interstate 80 is the second longest interstate highway in the U.S. Interstate 80, or I-80, is an east-west highway and one of the original routes of the Interstate Highway System.
I-80 runs from San Francisco, California to Teaneck, New Jersey. It also passes through major cities and closely follows the route of the first road for cars across the United States, the Lincoln Highway.
The highway first opened in 1956, but additions to the route didn’t finish until 1986. In some cities such as Youngstown, Ohio, motorists have to pay a toll fee to use the road.
Interstate 90 – 3,021 miles
The longest interstate in the U.S. is Interstate 90. Interstate 90, or simply I-90, is a transcontinental highway that connects Seattle, Washington to Boston, Massachusetts.
This highway connects 13 states, including Idaho, Montana, Wyoming, South Dakota, and more. I-90 also crosses New York by following Erie Canal. It also has 16 auxiliary routes in major cities like Chicago and Cleveland.
Established in 1956, Interstate 90 didn’t completely finish until 20Several sections of I-90 are are toll roads, while some sections, such as those in Pennsylvania and Wisconsin, remained toll-free.
U.S. Route 50 – 3,073 miles
With a length of over 3,000 miles, U.S. Route 50 is inching closer and closer to becoming the answer to what the longest highway in the United States is. U.S. Route 50, or simply U.S. 50, is an east-west U.S. highway from West Sacramento, California, to Ocean City, Maryland.
Built in 1926, U.S. Route 60 was part of the original U.S. Highway System. In 1986, the U.S. 50 received the name “The Loneliest Road in America” from Life magazine. The name refers to the Nevada portion of U.S. 50, which mostly runs across the desert, with little to no cities or communities in between.
U.S. Route 30 – 3,073 miles
What is the longest highway in the United States? Not U.S. Route 30, but it comes very close. In fact, U.S. Route 30 is the third longest U.S. highway.
Like all highways with numbers that end in “0”, U.S. 30 is a coast-to-coast route. It is an east-west highway that runs from Astoria, Oregon to Atlantic City, New Jersey. While I-80 closely follows the Lincoln Highway’s route, U.S. 30 comprises parts of the Lincoln Highway itself. Some areas even refer to U.S. 30 as the Lincoln Highway.
U.S. Route 6 – 3,207 miles
Back in 1936, if you asked someone what the longest highway in the United States is, their answer would probably be U.S. 6. U.S. 6, or U.S. Route 6, is a highway that connects Bishop, California to Provincetown, Massachusetts. It also passes by Nevada, Utah, Colorado, and several other states.
From 1936 to 1964, U.S. Route 6 was the longest highway in the United States. However, several modifications in California led to changes in the route, making it shorter. Because of this, U.S. Route 6 is now the second longest route in the United States.
Another name for U.S. Route 6 is the “Grand Army of the Republic Highway”. The name honors the Grand Army of the Republic (GAR), an organization of American Civil War veterans.
U.S. Route 20 – 3,365 miles
Last but not least is finally the answer to the question, “what is the longest highway in the United States?” The longest highway in the U.S. is U.S. Route 20 or simply U.S. 20. With a length of over 3,300 miles, U.S. 20 is an east-west highway of the United States Highway System.
As the “0” in its name suggests, U.S. Highway 20 is a major coast-to-coast route. It runs from the Pacific Northwest to New England. It starts from Boston, Massachusetts to Newport, Oregon, where it intersects with U.S. 101.
U.S. 20 first opened in 1926. Over the years, it received several extensions until it eventually became the longest road in the United States.
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