National Maximum Speed Law
![55 mph speed limit sign being erected in response to the National Maximum Speed Law.](/Images/godic/202501/09/Erecting_55_mph_speed_limit1621.jpg")
![In 1973, Congress enacted a national speed limit of 55 mph (90 km/h). Some states, such as Washington, enacted lower speed limits.](/Images/godic/202501/09/Speed_limit_50_19731621.jpg")
The National Maximum Speed Law (NMSL) in the United States was a provision of the Federal 1974 Emergency Highway Energy Conservation Act that prohibited speed limits higher than 55 miles per hour (90 km/h). It was drafted in response to oil price spikes and supply disruptions during the 1973 oil crisis.