Amtrak's Chicago-bound California Zephyr -- horn blaring, bells ringing, air hoses hissing -- rolls into Sacramento on time from the San Francisco Bay Area. "Booaarrd!" yells the conductor, and the silvery double-decker glides off. The train is carrying almost a full load of passengers, and after claiming one of the few unoccupied coach seats, I head for the dining car and a leisurely lunch as we snake our way up into the Sierra.

While the Zephyr winds along the edge of a steep canyon, my table companion, Channing Mercer, a retired homicide detective, munches on a chicken sandwich and peers down at the glistening American River. More than an hour earlier, we crossed it in Sacramento at an elevation of 14 feet above sea level. Now, the river resembles a thin green ribbon, nearly 2,000 feet below us. "Views like this are why I ride the train," says the bald ex-cop, who's returning home to Pittsburgh, Pa., after visiting his son in Martinez, Calif. It's only his third rail trip, but he says it won't be his last. "I got tired of taking off my shoes and belt buckle for the metal detectors at the airport," he says.

I'm here to get a firsthand look at how the trains are doing -- and what better place to start than Sacramento, terminus of the first transcontinental railroad? Think Golden Spike and 1869: the opening of the West. Since then, railroads, like much of the region, have gone through boom and bust. Now, though, they're making a heady comeback during these volatile energy-conscious times. Amtrak ridership, particularly in the West, is the highest since the government-run corporation was founded in 1971. Freight traffic on private railroads is up 90 percent since 1980. And Barack Obama, the first president of either party to voice strong support for Amtrak, says America's teetering infrastructure is a top priority in his economic stimulus plan. On the campaign trail, he advocated building high-speed passenger train corridors, and he and Vice President Joseph Biden, a longtime Amtrak commuter and advocate, took the train to D.C. for the inauguration.

The reasons for rail's resurgence aren't mysterious. According to a U.S. Department of Energy report last year, Amtrak consumes 17 percent less energy than airlines and 21 percent less than automobiles (based on the power needed to move a passenger one mile, in British Thermal Units). Rail travel emits 0.2 pounds of carbon dioxide per passenger per mile, compared to 0.9 pounds for an airplane and 1.6 for an SUV with a single occupant. A train can carry a ton of freight 431 miles on one gallon of diesel, about three times as far as a truck can. Then there's the backlash against growing congestion and aggravation at airports and on highways. "The public and political constituencies are finally realizing the need to do more with rail," says William Vantuono, editor of Railway Age magazine. "We are definitely in a railroad renaissance."

The Zephyr climbs over the craggy Sierra on the original transcontinental route. With all the tunnels and rights of way blasted out of granite -- at a rate of sometimes no more than two and a half inches a day -- it's easy to see why this is considered America's greatest engineering feat of the 19th century.

As the train descends along the shimmering Truckee River into the Great Basin, we watch the full moon rise while the sunset casts a pink glow and long shadows over Nevada's parched mountainscapes. "It's my first train trip, and it's awesome," says Cody Gazzaway, 19, of Lodi, Calif., who's on her way to visit her grandmother. "I was worried that if I took the Greyhound I would be stalked." She paid $74.96 for her one-way ticket to Salt Lake City: "It was much cheaper than Greyhound." Generally, though, Amtrak costs more than the bus, just as air travel tends to be pricier than the train.