The national 55 mph speed limit was signed into law by President Nixon on Jan. 2, 1974. In an effort to improve driving efficiency, the move was in response to a dispute with OPEC (The Organization for Petroleum Exporting Countries) that had led to an oil embargo on the US.
States were required to comply with the 55 mph limit to receive federal funds for highway projects. But the law was wildly unpopular and in many places enforcement was lax or non-existent. Studies found that over 80% of drivers violated the speed limit on many roads. In some states, such as Nevada and Arizona, laws were passed replacing speeding tickets with “energy wasting fines” of $5-15 as long as the driver did not exceed the speed limit before 1974.
The limit was eventually raised to 65 mph on rural highways and certain roads were allowed to have higher limits. In 1995, the national speed limit was repealed. Today, most Western states have maximums of 75 mph and the more densely populated Eastern states have 70 mph limits or 65 mph in the Northeast. Hawaii has a 60 mph maximum. Utah and parts of Texas have an 80 mph limit. And, some parts of Texas even have an 85 mph maximum.