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 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.
