The transcendent, still-wild network of national parks may be America's greatest gift outright to Americans. But as Sue Halpern reports, the monumental system, crumbling and compromised, demands rescue by each generation—including ours. Plus: The 10 greatest parks and how to visit them

Looking back, there were so many I'm not sure I could name the first one. National park, that is. Was it the Statue of Liberty, racing my brother through its hollow core up to the viewing platform in the crown, or the battlefield at Gettysburg, which that same brother claimed was full of ghosts? Was it the shell-cobbled seashore on Cape Cod, or the Everglades in a glass-bottom boat?

Memory strings them together with a single thread: Every summer our family would get in the car and go somewhere, and that somewhere was, without fail, a national park, monument, or historic site. "See America First" was a slogan still popular at the time, and to parents like mine, visits to the National Mall in Washington, D.C., and Cape Hatteras in North Carolina, and Appomattox Court House in Virginia—places where history had been made and heritage preserved—topped the domestic to-do list. It was part of our civic education.

The America I saw first was a narrow corridor that hugged the coast from Maine to Florida. The Grand Canyon, the Rockies, Glacier, Yellowstone, and Yosemite came later, and to an Easterner like me they were a revelation about scale and biodiversity and grandeur and, eventually, inheritance: These gorgeous places were mine. And yours. They were ours together. Not that I thought much at first about how we came to acquire them or what it took to keep them up. In that, it's safe to say, I was a typical American.

Blissful ignorance takes us only so far, however, and over the past two decades—as millions of visitors were stopping their vehicles in Yellowstone to watch gray wolf pups frolicking on a knoll, or tramping across the snowfields at Glacier under a hot summer sun, or peering into the Precambrian past from the North Rim of the Grand Canyon—the parks have been in decline. Aging infrastructure coupled with diminishing operating budgets led to a massive maintenance backlog and contributed to reduced hours, suspended interpretive programs, and ranger layoffs. By the time the Obama administration took office, there was upwards of nine billion dollars' worth of roads and restrooms and trails and sewage systems and dams and benches and walkways in need of repair or replacement. Our national heritage had a rotting foundation and a leaky roof, and in the race between time and money, time was winning.

In an odd way, the billions of dollars in deferred maintenance is the measure of a certain kind of success: It represents a burgeoning inventory of places and structures—the National Park Service (NPS) now runs 391 "units"—and the torrent of traffic visiting them. As Robin Nazzaro, the head of the Government Accountability Office division that oversees the national parks, points out: With 27,000 structures, 15,000 miles of unpaved trails, 3,565 miles of scenic trails, 1,804 bridges and tunnels, 776 campgrounds, and 505 dams, "that's a lot of infrastructure to support."

Yet even to those of us who've hiked down into the Grand Canyon in the past few years only to find trails closed off with yellow caution tape, or who've tripped over the rickety walkways at Old Faithful, it might not have been clear that we, the people, were in danger of squandering what we mindlessly consider our birthright. How easy to forget when mesmerized by the rush of Yosemite's Vernal Falls, or floating down the Snake River under mountains that define the word iconic, that the parks are not just a symbol of our 233-year-old national experiment but a tangible expression of American history, both human and wild, and that all this tangibility costs money. So on Earth Day this year, when Ken Salazar, the new secretary of the Interior, announced that more than $900 million of the American Recovery and Reinvestment Act—what is commonly called the stimulus—was being released immediately to the parks, he was offering to do a lot more than fill in a bunch of potholes.