Like the grizzled prospectors who were among the first white people to tread in what are now our national parks, you can find valuable nuggets traipsing through the gorgeous, vast expanse of Ken Burns' latest epic, The National Parks: America's Best Idea.

It starts tonight at 8 on WHYY TV12 and runs for 12 hours, in six, two-hour installments, big-footing the entire PBS prime-time schedule this week, as each episode is rebroadcast nightly at 10. There will be marathon rebroadcasts next weekend, too.

America's Best Idea is an extensive examination of the history of the national parks movement and of many of the parks themselves, complete with old-time photos and film and loads of contemporary scenic footage, too. It's all arranged to support Burns' sometimes heavy-handed thesis that the democratization of our nation's most gorgeous and historic lands is a key to our national culture.

One of the mob of writers and historians actually says, "America's nature is the guarantor of America's constitutional freedoms. If you don't have a genuine link to nature in a serious, even profound, way, you can't be an American."

If you can't find flaws in 12 hours, you're not much of a critic. It's also annoying, for instance, that Burns, or, more specifically, his writer-collaborator, Dayton Duncan, gives a 38-word paean to the ancient bristlecone pine without noting that the oldest ones aren't even located in a national park. They also make a big deal about how national parks saved the bison, without citing the important role of some state parks, such as South Dakota's Custer State Park.

But the good - the beauty shots alone - far outweighs the bad.

My favorite nugget concerns the Kolb brothers, Ellsworth and Emery, who emigrated to the Grand Canyon from western Pennsylvania just after the turn of the 20th century, and ran a photography business on the Bright Angel Trail.

With their cumbersome equipment, they would shoot tourists on their mules near the top of the trail - "wall-eyed" and "typhoid pale," according to humorist Irvin S. Cobb of Paducah, Ky., narrator Peter Coyote tells us - then run 4 1/2 miles (and 3,000 vertical feet) down to the nearest clean water to develop and print the photos, then run back up to sell them. They did that for 29 years, until running water was brought to the South Rim.

They made a mint, and Emery worked at the studio, which is still there, until he died in 1976. "The Grand Canyon. It's my religion," Emery once said, in one of the few national parks comments ever made that's not in Burns' documentary

The daredevil Kolbs did lots of other neat and important stuff, but I don't have 12 hours.

There are scads of contemporary characters interviewed about the parks, too, such as J.L. Crawford, born with the help of a midwife in 1914 near what is now the headquarters of Zion National Park, who made up his mind to join the park service because rangers "were dressed nicely and had a good job."

And of course, veteran park ranger, poet, and storyteller Shelton Johnson, who, apparently, wasn't much of an American growing up in Detroit, but was fortunate to get park work. His comments help buoy the entire enterprise.

Burns, as usual, seems to go into everything, creating an amazing documentary of about 150 years of history (he stops in 1980), illuminating the lives of little-known, yet toweringly important figures (and blackguards as well) and taking us to dozens of parks. But, as usual, it's more archive than TV show, as, once again, you wonder why somebody, or Burns himself, does not trim his output to four or five hours for broadcast and let those who are really interested go out and buy the sunrise-to-sunset director's cut on DVD.

Television

The National Parks:

America's Best Idea

Begins at 8 tonight on WHYY TV12

Contact television critic Jonathan Storm at 215-854-5618 or jstorm@phillynews.com. Read his recent work at www.philly.com/inquirer/columnists/jonathan_storm/