What: The Mount St. Helens National Volcanic Monument, a 110,000-acre area set aside for natural observation after this happened on May 18, 1980:

Why: The eruption of Mount St. Helens was the most cataclysmic North American volcanic episode in almost a century. It killed 57 people, and every bird, every fish, and every mammal bigger than a field mouse within a couple dozen miles. It destroyed a lake and 185 miles of roads, and deposited sheets of ash across the state. In the aftermath of such an epic disaster, the natural human reaction is to clean the place up. Not this time. The Reagan administration did a lot of awful things, but one great thing they did was set aside the area surrounding Mount St. Helens as a monument. What this meant was that with the exception of necessary demolition, the aftermath of the volcano would be left the way it was. Trees stayed down. Lakes stayed buried. And, on its own, everything came back.

Impact: That tan area is where you can't go. It shows where the north face of the mountain slid into the valley. As you drive through the area, you wonder, why are these trees still down? But then two chains of thought hit you: First, that it happened, and then how much of it happened, and then how it could happen again, but just up the road at Mount Rainier, when Seattle disappears from the earth. And second, that those deer you're seeing among the overgrowth are proof that no matter what happens, life goes on. Even if lahars flattened Seattle, we'd just make another one.

Personal Connection: I was 12 1/2 years old. I was on the phone with my dad when I felt the house rumble and shimmy. I said, "Dad, gotta go," and ran outside to see a mushroom cloud blackening the left half of the sky. I assumed what everyone assumed: the Russians just blew up Portland. That morphed to: the Hanford nuclear reactor just went airborne. And that finally settled into: wait, wasn't there something on the radio about a volcano? And so we watched the skies, and waited for the cloud of smoke and ash to bury Seattle. And it never came. The wind took the ash east to Spokane, and even little bits of it fell on Providence. But we Seattleites had to buy vials of ash from shops in Chehalis rather than dig out from our own. Some of us, preposterously, felt cheated.

Other Contenders: the Jefferson Memorial, our most beloved vault of reason; Ground Zero, which I visited weeks after the fall, and hope never to see anything built upon; the Crazy Horse Memorial, which maybe I'll see finished, and maybe I won't; the U.S.S. Arizona, which remains submerged along with the hopes of world conquerors everywhere.