U.S. Interstate Highway System

Read the map by its numbers.

A reference atlas for the U.S. Interstate Highway System. Search active mainlines, read the logic behind every route number, and explore each corridor in detail.

Browse the database Decode a number

71active numeric mainlines

901possible number slots, I-1 to I-999

10Hawaii, Alaska, and Puerto Rico routes

23notable auxiliary examples

What's new

Faster ways around the atlas.

A few new tools to move through the system more quickly.

Quick search

Press / or ⌘K anywhere to jump straight to any route by number.

Save your routes

Bookmark routes with the Save button and find them back here on the home page.

Share & randomize

Copy a direct link from any route page, or hit Random route to explore something new.

Connecting routes

Every route page now maps the Interstates it meets — follow the shields across the network.

Three ways in.

Search the full index, decode a single number, or learn the rules that govern the whole grid.

Search the database

Every active route plus every theoretical number slot from I-1 to I-999, filterable by type, status, and corridor.

Open the database

Decode a number

Enter any designation and read what it means: direction, parent route, and whether it is a loop or a spur.

Read the numbering guide

How the grid works, why odd and even numbers point in fixed directions, and the exceptions that break the rules.

Featured corridors

A few routes to start with.

From the longest Interstate to the shortest two-digit route. Open any card for its full record.

Seattle to Boston.

Miami to Houlton.

Santa Monica to Jacksonville.

2,460.2 mi

I-5 North-south

San Diego to the Canadian border.

1,381.2 mi

I-70 East-west

Cove Fort to Baltimore.

2,170.9 mi

I-97 North-south

Annapolis to Baltimore.

17.6 mi

See the full route directory

Every number, in one index.

Active mainlines, federal programs, notable auxiliaries, and every theoretical slot from I-1 to I-999.