Speed limit laws, which date to 1901, traditionally have been the responsibility of the states. In 1973 Congress responded to oil shortages by directing the U.S. Department of Transportation to withhold highway funds from states that did not adopt a maximum speed limit of 55 mph. Before that, speed limits on rural interstates in most states ranged from 65 to 75 mph, with the majority of states setting rural interstate speed limits of 70 mph. In urban areas, most states maintained 55 mph speed limits before the national maximum speed limit was established.
By March 1974, all states adopted the 55 mph national maximum speed limit. Concerns about fuel availability and costs faded, however, and Congress in 1987 allowed states to increase speed limits on rural interstates to 65 mph.
The National Highway System Designation Act of 1995 repealed the maximum speed limit, allowing states to set their own limits for the first time since 1974. Many states quickly moved to raise speed limits on both rural and urban interstates and freeways.
There has been a trend toward higher speed limits on freeways and interstates in recent years. Currently, 21 states have maximum speed limits of 70 mph and 12 states (Arizona, Colorado, Kansas, Louisiana, Maine, Montana, Nebraska, Nevada, New Mexico, North Dakota, Oklahoma and Washington) have maximum speed limits of 75 mph on some portion of their roadway systems. On some sections of interstates in five states (Idaho, South Dakota, Texas, Utah and Wyoming) speed limits are 80 mph. In October 2012, a 41-mile stretch of Texas 130 opened with a speed limit of 85 mph.