If you are an aficionado of the classic American roadside diner, put the Salem Diner on your must-visit list. It is a blue-plate beauty, opened for business on July 3, 1941, and built to look as futuristic as a streamliner locomotive or airplane. At the time, it was the height of modern design. Sixty years later, it has become a relic of a time when going places fast seemed the ultimate sign of progress, and it is now on the National Register of Historic Places.