Since the early 2000s, Interstate Guide has documented America's Interstate Highway System through photography, route histories, business routes, and reference material. The site covers both the familiar and overlooked parts of the national network.
Browse Interstate highways by route number or state, explore historical features and trivia, follow proposed corridors, and discover the stories behind the roads that connect the country.
Explore Interstate Guide
Browse Interstate routes, discover business loops, explore historical features, and follow the continuing evolution of America's highway network.
✓ Mainline Interstates
✓ Auxiliary Routes
✓ Future Interstates
✓ Former Routes
✓ Unsigned Routes
✓ Business Routes
Browse by Route Number
Interstate families and branch routes.
Browse by State
Routes organized geographically.
Business Routes
Former alignments and downtown connectors.
Features
History, trivia and numbering guides.
What's New
Recent additions and updates.
About Interstate Guide
Contributors and project history.
The Interstate Highway System has evolved substantially since the early years of completion. Today the system continues to grow with new corridors developed with Congressional authority, such as I-69 between Texas and Indiana, the completion of I-49 in Arkansas and Louisiana and the southern extension of I-27 from Lubbock to Laredo, Texas. Interstate Guide documents both the original network and the routes added through decades of expansion.
Interstate Guide currently documents:
Interstate Numbering Guide
Numbering guidelines for the Eisenhower Interstate System. Why is there an I-238 but no I-38? Read More →
Proposals and Unbuilt Routes
Previously proposed or suggested long distance and regional Interstate corridors that were never realized or otherwise remain unconstructed. Read More →
Recent Updates
Fired up the scanner and added two maps showing the proposed alignment of Interstate 178 into Allentown, Pennsylvania.
2026-08-11 16:06:47
Updated coverage of both ends with photos from July 25, 2024. Added a scanned map from 1975.
2026-08-11 12:03:54
62 miles of U.S. 15, between I-180 in Williamsport and the New York state line near Lawrenceville, Pennsylvania were officially redesignated as part of Interstate 99 on July 30, 2026. Construction upgrading the exchange where the end of I-99 ties into I-80 near Bellefonte, PA continues to 2030. Added or replaced coverage at both at the south end near Bedford and at I-80 with photos from July 14 and July 25, 2024.
2026-08-11 11:18:03
Interstate 777 is a designation promoted by the Carolina Core initiative of the Piedmont Triad Partnership for the freeway along U.S. 421 between I-77 near Hamptonville and I-40 and Salem Parkway in Winston-Salem. The same group successfully advocated for an Interstate designation (I-685) along the U.S. 421 corridor between Greensboro and Sanford.
2026-08-10 11:59:33