Along the way, the museum covers the main questions and raises a few you might not think to ask.

Who started the Pony Express? Russell, Majors & Waddell, the leading freight-hauling and military supply company in the West. And the Pony Express' official name was the Central Overland California & Pike's Peak Express Co.

By 1860, it was well understood that the train and telegraph would soon connect California with the East, knitting North America together with a new intimacy. But in the meantime, there were prospectors and settlers desperate to be in touch with the East, and there were government men eager to nudge the populace westward. Also, with the Civil War threatening, Northerners were eager to forge more direct connections with California, cutting Texas and Arizona out of the action.

On Jan. 27, 1860, partner William Russell sent a telegram to his son: "Have determined to establish a Pony Express to Sacramento, California, commencing 3rd of April. Time ten days." This gave the newborn company all of 67 days to hire riders, establish stations and buy horses.

How long was the route? Estimates vary, as did the riders' routes. Some say 1,840 miles. Some say 1,966.

How many riders did it take to get a letter from St. Joe to Sacramento? About 25, usually riding 75 to 100 miles each.

Did the transcontinental train kill the Pony? No. The train didn't go through until 1869.

But the first coast-to-coast telegraph message went through in October 1861, and the last Pony letters were delivered the next month. Russell, Majors & Waddell went into a corporate death spiral. The St. Joseph stables burned in 1888, were rebuilt with bricks, fell to other uses, then fell idle for years until a local philanthropist bought the site. (The museum opened in 1959 as a subsidiary of the St. Joseph Museum, then broke off on its own and expanded in the 1990s.)

From the stables, it's just a few blocks east to the Patee House Museum. This four-story brick box of a building, which dates to 1858, must have once seemed the center of American civilization west of the Mississippi. But when I stepped up, the front door was locked.

Not enough volunteers, director Gary Chilcote told me when I called on my cellphone. Then he opened up for me.

"It was a hotel three times and a girls' college twice, and it was a shirt factory for 80 years," Chilcote said, striding room to room, turning on lights.

The building became a museum in 1963 and Chilcote, 75, a longtime reporter and editor for the St. Joseph News-Gazette, has been involved since the beginning. He runs it with help from family members and estimates 20,000 visitors last year.

He set up the ground-floor Pony Express office area to look as it might have 150 years ago. He has trains, including a mail-sorting car from 1862. He has buggies, cars and fire trucks. He has an upstairs ballroom where authorities held court during the Civil War (and condemned seven men to be hanged across the street). He has a working carousel from 1941, a bar where you can order sarsaparilla, a 1,000-pound ball of yarn and weapons used in long-ago local homicides.

"You understand," he says conspiratorially, "that what we're doing here is writing feature stories and putting them in a case."

Before heading west, I felt my way to the river's edge, where the Remington Nature Center opened next to Terrible's Casino in 2008. The river was at my feet, plain and brown and running fast. If I looked straight across to the thickets on the other side, I could almost imagine some terrified teenager on horseback, galloping off into who knows what.

About four days and 1,000 miles west of St. Joseph, Pony riders would carry their letters down out of the Wasatch Range and show up at 143 S. Main St. in Salt Lake City, the Salt Lake House Hotel.

The city of Salt Lake in 1860 was younger than most of the Pony's riders. But already, Salt Lake had about 8,200 residents and it was growing fast.

The Mormon faithful, who had been expelled from Missouri in the 1830s and driven from Illinois in the 1840s, were busy sinking roots. They farmed, practiced polygamy (which wouldn't be banned for 30 more years) and slowly but steadily carted and stacked granite blocks to build a temple in the middle of town.

Many Mormon boys rode for the Pony and probably had the chance to gallop near the spot where Brigham Young in 1847 declared "This is the place." From the Wasatch range, the route led right down Main Street and out to Camp Floyd, 40 miles southwest, where 3,500 federal troops — nearly a third of the U.S. Army — had been stationed in case the Mormons rebelled. (They didn't. The camp is a state park now, with a little museum in the old Army commissary building.)

These days, Salt Lake City is home to about 180,000 people, about half of them Mormon. On the spot where Brigham Young made his pronouncement, visitors now find This Is the Place Heritage Park, a 450-acre pioneer history park. Costumed staffers tend to 19th century chores. There are pony rides, a petting zoo, historic buildings, and statues celebrating the Mormon pioneers and the Pony Express. Every day in summer, a latter-day Pony rider dashes through.