LOS ALAMOS, N.M. — Tucked away in one of northern New Mexico’s pristine mountain canyons is an old log cabin that was the birthplace not of a famous person, but a top-secret mission that forever changed the world.

Pond Cabin, along with a nearby small and stark building where the second person died while developing the nuclear bomb, are among a number of structures scattered in and around the modern day Los Alamos National Laboratory that are being proposed as sites for a new national park commemorating the Manhattan Project.

It’s an odd place for a national park, many admit. Besides the fact that some of the sites are behind the gates to what is supposed to be one of the most secure research facilities in the world, nuclear critics have called the plan an expensive glorification of an ugly chapter in history....