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.