Numbering the Highway System
Updated February 21, 2017 | Factmonster Staff
![Updated by an Factmonster Editor on February 21, 2017](/themes/ip/images/info-circle.png)
Knowing your numbers helps you know which direction you are going on U.S. highways. Here's how the highway systems are numbered.
Interstate Highways
Three highways run from coast to coast: I-10, I-80, and I-90. Seven highways run from border to border: I-5, I-15, I-35, I-55, I-65, I-75, and I-95. |
- The interstate system totals 46,300 miles. All interstate highways are marked by blue signs with red tops.
- The north-south highways have odd numbers with 1 or 2 digits, usually including a 5. The lowest numbers are on the West Coast and increase as they move east. For example, I-5 is on the West Coast, I-95 on the East Coast.
- The east-west highways have even numbers with 1 or 2 digits. The lowest numbers are in the South and increase as they go north. For example, I-4 runs through Florida; I-96 is the northernmost route.
- An interstate highway with 3 digits is a connector or offshoot of a main route.
U.S. Routes
- U.S. routes are posted in black letters on white signs.
- The north-south routes have odd numbers, with 1 to 3 digits. These numbers increase from east to west (just the opposite of the interstate system). For example, U.S. 1 runs along the East Coast; U.S. 101 runs along the West Coast.
- The east-west routes have even numbers, with 1 to 3 digits. The lowest numbers are in the North and increase moving south (just the opposite of the interstates). For example, U.S. 2 runs along the Canadian border; U.S. 90 runs through Texas.
For the distance between many U.S. cities, see Road Mileages Between U.S. Cities at Infoplease.com.
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