Standing in Idaho City's dirt-lined, deserted Main Street, it's tough to imagine how it was 140 years ago. With more people than Portland and over 250 thriving businesses, it was a bawdy, lusty town where whisky was cheaper than water  -  and life cheaper still. Why did more than 12,000 (mostly) men rush to this nascent  -  and very temporary  -  metropolis? The same lure that drew thousands to Alaska and the Yukon. Up in them thar hills, in 1862, prospectors discovered gold...

By 1865 most of the gold in the Boise Basin was gone, as was much of Idaho City. A comprehensive fire leveled the town and the prospectors moved on. But in that short time, more gold was pan-ned than in the Alaska Gold Rush  -  over $ 250,000,000 worth. Now the city's just a tourist stop on Idaho's Ponderosa Pine Scenic Byway.

Boise to Boise or Bust

The Byway, Highway 21, is the first leg of our tour of Southern Idaho, and rises into the Sawtooth Range from Boise. When French-born Captain Benjamin Bonneville of the US Army arrived at the site of Idaho's modern-day capital, he is said to have named it la rivière boisé, or the wooded river. Boise is still known as the City of Trees; and a river, the Boise, still runs through it.

The first section of the Byway to Lowman is a narrow winding two-lane that swings through a succession of small communities, these becoming fewer as the road climbs. The afternoon sun throws short, severe pine-tree shadows onto the tarmac as we climb into the mountains, making it trickier to judge a clean line through each bend. The surface has suffered frost heaves and the ravages of snowplows; narrow cracks and potholes are repaired hastily with tar stripes. Our wheels follow ruts and slide on the tar.

In July 1989, lightning strikes ignited a fire that devastated the pine forest. When the smoke cleared, more than 46,000 acres of the Boise National Forest had burned. At Lowman, the road widens, and, though less curvy, the surface is in much better repair. We pass Kirkham Hot Springs, one of more than 200 in Idaho and swing quickly along the achingly pretty Payette River (named for Francois Payette who ran the Fort Boise trading post in the 1840s). The Payette eventually joins the Salmon River, a tributary of the Snake, which in turn feeds into the Columbia. But we're following the Payette's south fork upstream, high into its source in the Sawtooth Range. Twenty-one eventually drifts away from the Payette and the climb begins in earnest. The first pass on the road is Banner Summit at 7,000 ft.

May is usually a good time to tour in Idaho. The winter snows are gone from the roads, yet the mountains still wear a fresh coat of the white stuff, while the bad weather stays in the Cascades closer to the coast. But a freak winter storm pushing down from Canada and record low temperatures have delayed the thaw, dumping fresh snow on the pass. We're about 24 hours behind the weather, and mercifully, strong spring sunshine in the storm's wake has stripped the snow from the road  -  though at the Pass a deep blanket covers the surrounding prairie.

The first stunning sight of the Sawtooths jolts the visual cortex. As the trees part, the range pops up from the snowy plain like the back of a giant white stegosaurus, its frozen ridges slicing into the deep indigo sky. Stanley is a mountain resort town, pretty as a postcard, with the Sawtooth Range's razorback as its backdrop, and it's our first night's stopover. The Mountain Village Inn serves us succulent hamburgers as the setting sun flushes the mountains with its pink glow. As we retire, we resolve to ride out before breakfast to catch the sunrise.

Geoff, my riding partner, is awake before I am, and we hit the road at six-thirty. Though the temperature is in the low 20s, the road is free of frost  -  though not our bikes, and I envy Geoff his K1200GT's heated seat. We return to the Inn somewhat cooler, and I risk a plate of biscuits and gravy  -  a dish that can be a catastrophe if prepared badly. It's excellent, the biscuits crisp yet fluffy, and the gravy savory and hot.

Our destination for the day is Montpelier, a small town in southeast Idaho close to the Utah border. But our first order is to crest Galena Summit at 8,700 ft. The road from Stanley is fast and wide for 20-or-so miles, and then climbs steeply. Hairpin turns connect the straights that switchback up the mountainside. At the summit, the road winds between snowy ridges before opening out into the vast plain of the Salmon River. Before feeding into the Snake, the Salmon meanders 420 miles, draining vast watersheds as it goes. Only in the 1950s did the Salmon become navigable upstream; previously it was known as the "River of No Return."

From Galena, the road drifts gently down towards Ketchum, the base town for Sun Valley ski resort. Downhill racer Picabo Street grew up here, in the tiny mountain community of Triumph, taking her name from the nearby town. Our route calls for a shortcut to Picabo from Bellevue. It's a small road and difficult to find, so we ask for directions.

Pioneer Trail

We're now heading east on Highway 20, which connects Mountain Home with Idaho Falls across Camas Prairie and the Snake River Plain. In the days when thousands of pioneers traipsed across the west to Oregon, this route was known as "Goodale's Cutoff."

Most migrants crossed Idaho by a route south of the Snake River. But in July 1862, fur trader Tim Goodale set off from Fort Hall on the Snake River leading a wagon train party that numbered almost 1,200 at its peak. His route crossed the Snake River Plain past Southern Butte to Lost River, then across Camas Prairie to rejoin the Oregon Trail at Ditto Creek. The route became popular as a shortcut  -  and because it steered clear of the scene of an Indian ambush at Massacre Rocks on the southerly Trail.

This is high prairie, and the road is fast and wide, but we pull over to check out the Craters of the Moon national historic monument. In prehistoric time, lava forced its way through the ground here and spread over the surface, creating an eerie honeycombed crust of brown rock like the inside of an Aero chocolate bar. A similar phenomenon created the "ice" caves near Shoshone.