Before 1974, the speed limits across the United States varied by state.  Some states allowed speeds up to 80 miles per hour. However, President Nixon had different ideas.

On this day, January 2nd, in 1974 – President Nixon signed into law a highway speed limit across the United States of 55 miles per hour.

This law was not motivated by safety.  Instead, Nixon signed this law because it was widely thought that higher speeds were not fuel-efficient.  And in an effort to limit US need for foreign oil – the Nixon Administration was very vocal about fuel rationing and this law was one of many strategies employed to try and achieve this.