Interstate 35 is the central north-south freight backbone of the United States, running 1,568 miles from Laredo, Texas at the Mexican border to Duluth, Minnesota on Lake Superior. It is the busiest land port-of-entry corridor with Mexico — Laredo handles more cross-border truck traffic than any other US port — and the only interstate that splits into two parallel routes (I-35E through Dallas and I-35W through Fort Worth in Texas; I-35E through St. Paul and I-35W through Minneapolis in Minnesota).
The route is the spine of the NAFTA / USMCA freight network. Auto parts, electronics, and produce flow north from Mexico through Laredo into the Texas Triangle, the Kansas City and Des Moines logistics hubs, and the Twin Cities. South-bound flows are dominated by grain, machinery, and raw materials. Texas DOT data routinely shows I-35 segments through Austin, Dallas-Fort Worth, and the Hillsboro split among the highest truck-volume corridors in the United States.
Geographically I-35 is mostly flat with rolling terrain through the Texas Hill Country, a long climb over the Wichita Mountains in southern Oklahoma, and gentler rolling country through Kansas, Missouri, Iowa, and Minnesota. Weather hazards skew toward severe thunderstorms, tornadoes (the corridor crosses the heart of Tornado Alley between Oklahoma City and Wichita), and winter ice across the central Plains.
- Busiest US interstate for cross-border truck traffic with Mexico (Laredo)
- Splits into I-35E and I-35W in both Texas (DFW) and Minnesota (Twin Cities)
- Crosses six states: TX, OK, KS, MO, IA, MN
- Designated NAFTA / USMCA priority freight corridor
- Concurrent with no other interstate for any significant distance
- Heaviest single-corridor truck volume in central US
- Crosses the Red River at Gainesville/Marietta and the Mississippi at St. Paul