The 55 mph limit was abolished by the Republican Congress in 1995 and signed into law by Bill Clinton.
During Reagan's second term in 1986, states were given the right to set the 55 limit to 65 on interstate highways in areas defined as rural by federal regulation.
Your memory is better than mine, I remember Jimmy Carter wondered how he could have gotten beaten by a man who ran against the speed limit.
I know, I remember how big an issue it was, especially for truckers whose machines were optimized for the higher speed. I say that because this late in life some things I know to be true, are not true, except in my own memory, so I should do a little more research before I jump.
Getting old is mostly a little better than the other option.