National parks have been set up for mountains, rivers, caves, rock formations, glaciers, forests, canyons, fossils, deserts, hot springs and volcanoes. Now, lawmakers have decided that the nation needs one for the atom bomb.

On Friday, the Senate joined the House in passing legislation to establish the Manhattan Project National Historical Park, memorializing the secretive World War II effort that involved some of the world’s top scientists and, in total, more than a half million Americans. The park will protect hundreds of surviving buildings and artifacts across three states — New Mexico, Washington and Tennessee — where the first bomb came to life 70 years ago.

The sites vary from the rustic home of J. Robert Oppenheimer, the project’s scientific head, to a pioneering reactor that made nuclear fuel, to a large Quonset hut for bomb assembly.

The measure awaits President Obama’s signature, which is expected this week.

Cynthia C. Kelly, president of the Atomic Heritage Foundation, a private group in Washington, D.C., said she had worked on the preservation plan for 15 years and was thrilled it had finally come to pass.