Not all historic sites are in parks or in public places. Many are privately owned and many are located on private property and cannot be viewed by the public, even if people know that they exist and know where they are.
But some historic places are businesses that are still in operation and open to the public. The place or building usually has to be old to be considered historic.
But just being old does not mean that anyone is interested in it unless something famous or unusual happened there.
Or if the place itself is built or designed in a different or unusual way for its use or for the area that it is in.
There is such a place in Drake, Missouri, that is still open and still operates as a gas station, convenience store, and restaurant.
It is the Old Dutch Mill on U.S. Highway 50.
It meets the criteria of being old and being built in an unusual fashion. The Old Dutch Mill was built in 1934 and is designed to look like an old mill.