Tonight Michael Portillo continues his rail journey along the Upper Mississippi and finds out how engineers in the 19th century made the Mississippi navigable, before joining in the dancing at a tribal gathering of the Dakota Sioux.
The US boasts some of the best train trips in the world, whether your taste is for history like Portillo, or you're partial to mountains, coasts or vintage trains. Here are a few of our favourites.
The California Zephyr: Chicago to San Francisco
This is a top contender for the most scenic railroad in North America. The 2,438 mile-journey takes you through the Rockies, the canyons of the Colorado River, the plains of Nebraska and the snow-capped Sierra Nevada mountains. It takes two days so be sure to book a sleeping car.
The Coast Starlight: LA to Seattle
The 1,377-mile, 34-hour Coast Starlight links the cities of the West Coast and is up there with the California Zephyr for spectacular scenery: the Diablo mountains, California's great valleys, San Francisco Bay, the Cascade Mountains, the jagged cliffs and fog-shrouded peaks of the Pacific Ocean shoreline. Book a seat in the Sightseer Lounge Car for the best view.
The Southwest Chief: Chicago to LA
It takes 43 hours to do this 2265-mile trip. If you just want to do the most scenic section, skip the Mississippi and the plains and board at Trinidad, Colorado. From there, the train passes through the Sangre de Cristo mountains (and some of the last semaphore signals in use on American railroads), New Mexico's highlands and the Rio Grande. Disembark at Williams Junction, Arizona, for a bus connection to the Grand Canyon's century-old vintage railway – a two-hour trip with musicians and actors who tell tales of the Wild West.
Back on board the Southwest Chief, you'll chug through canyon passes only a few feet wider than the train, the Mojave Desert and Cajon Pass, before arriving in LA.
Radio Times Travel: Steam Railways of Austria, 7 nights from £679pp
The Durango and Silverton railroad: Durango, Colorado
The Durango and Silverton Narrow Gauge Railroad – to give its full name – was constructed in 1882 to haul gold ore from southwest Colorado's San Juan mountains. Nowadays, it's the view that is precious. The coal-fired, steam-powered locomotive winds climbs 3,000 ft through the two-million acre San Juan National Forest, affording stunning views of its canyons and 14,000 ft peaks. The round-trip takes a day, including a two-hour stopover in Silverton. Reserve a seat in the "Historic Narration Car" to hear tales of yesteryear from actors in period costume.
Napa Valley Wine Train: Napa, California
The civilised way to see America's most famous wine region is aboard the vintage Napa Valley Wine Train. A variety of trips are available, offering guided tours and tastings at wineries, and seasonal special events and talks. While the sun-drenched vineyards roll by, passengers are served a gourmet dinner with a glass of wine, naturally.
Great American Railroad Journeys is on weekdays on BBC2 6.30pm
Radio Times Travel holidays:
Scottish Highland Railways, 4 nights from £459pp. Visit the heart of the Highlands to enjoy three spectacular train journeys. Ride the famous West Highland Line from Fort William to Mallaig, take a trip on the charming Strathspey Steam Railway and enjoy a breathtaking run from Inverness to the Kyle of Lochalsh. Click here for more details and to book
Historic Railways of the Isle of Man, 4 nights from £499. Join us for a marvellous short break to a place where life is lived at a slower pace, against a background of rolling hills and wonderful beaches blessed by clean air and unpolluted skies. An independent Crown dependency, the island is full of fascination - its unique heritage railways offering a marvellous way to discover and explore. Click here for more details and to book
Steam Railways of Austria, 7 nights from £679pp. Join us in the scenic Austrian Tyrol, where in addition to a stay in a wonderful Alpine paradise, you'll enjoy journeys on some delightful vintage railways, and a visit to Imperial Innsbruck, the glorious Tyrolean capital. Enjoy all the delights of a welcoming, traditional hotel, and in addition to the included tours, join some wonderful optional excursions. Click here for more details and to book