Copyright © 2008, Doug Wade
Note that it was the first nuclear power plant in the sense that it was the first time they took a reaction and actually generated electricity out of it (instead of just heat). It was also the first breeder reactor as well as a bunch of other firsts (all kinds of problems have to be solved when you're running something like this on an ongoing basis). They ran it from 1951 to 1964.
This sign was rather reassuring since most of the Idaho National Lab is still active and there's just this one little side road that takes you to this building. You go on in and there's your choice of the self guided tour or a tour guide.