What is the typical speed limit on a US Interstate highway in most states?

Interstate speed limits vary by state and by specific road section. Most US states post Interstate limits in the 65-75 mph range. Some western states allow 80 mph on rural Interstates (Texas, Utah, Idaho, Montana, Wyoming, Nevada, South Dakota). Texas has a 85 mph posted limit on some rural toll roads — the highest in the country. Within urban areas and through cities, Interstate limits typically drop to 55-65 mph. No US state has unlimited Interstate speeds; the federal government previously imposed national 55 mph and 65 mph caps, both later repealed, leaving the matter to individual states. Always check the specific posted limit for the section you are driving — limits change without obvious markers.