Driving up the mountain, Karen Hirsheimer knows she's nearly home when the potato chip bags explode. "Suddenly there are chips all over the car." Exploding chip bags, cigarettes that snuff themselves in ashtrays, woozy mosquitoes and tepid boiling water are part of life in Leadville, America's highest city.

With only 25 percent of the atmospheric pressure available at sea level, strange things happen here. Bread doesn't rise, golf balls fly farther and the high school track team, bursting with extra red blood cells, dominates cross-country running whenever it competes below. At the Safeway, ice cream pushes out of containers and vacuum-packed snacks sit like fat balloons on the shelves. Mosquitoes, should one arrive, are so groggy that locals admit feeling pity as they swat them. "They are so slow you can see them coming," said Andy Locke, a surveyor. "It's almost sad."