FAIRFIELD — It used to be that pony express riders had to fear highwaymen, Indian attacks, severe weather and hostile wildlife as they rode furiously to move the mail from California to Missouri. They carried pistols and rode through the black night for long stretches without encountering another human being.

Today, they're watching out for crazy drivers, semis and potholes in the road. They're being tracked by GPS units and watched from above by satellite.

Nevertheless, it's still a thrill to ride horseback on the historic 1,966-mile stretch from San Francisco to St. Joseph, Mo., carrying a leather pouch full of letters.

"It's fun," said 18-year-old Adriaan Riet from Fairfield, as he dismounted from his 2-mile stretch in the western desert flat. "Although I had to dodge a couple of bushes back there."

In his red shirt, bright yellow scarf and cowboy hat, Riet looks every inch the pony express rider of old (except for the braces on his teeth) and he says he would have been one if he'd been born a few years earlier.

Riet loves the re-ride and has been participating since he was 14. Sunday, he rode under blue skies, hot sun and in 80-degree weather, but he's ridden in snow and rain.

"One time, I had to ride downhill on I-80 when it was raining hard!" he said.

The modern-day riders worry about rain because the horses can slip on slick pavement. They also worry about today's drivers and new riders who may not be prepared for a horse to startle at a backfire or loud engine.

"Idiots and cars, that's our biggest concern," said Eric Arnesen of West Valley. Arnesen, his daughter and son-in-law, Kyle and Racheal Arnesen from Lindon and his grandson, Jeremy B. Arnesen, are all riding in the 148th annual re-ride.

"Potholes? There were some beauties this morning on my ride from Simpson Springs," Arnesen said.

It takes more than 500 riders and horses to recreate the ride, which was run for 19 months from April 1860 to November 1861 by boys and men who were willing to take risks working for the Central Overland and California Pikes Peak Express Company for $24 a week.

Want ads at the time called for "young, skinny guys not over 18. Experienced riders. Orphans preferred."

The goal was to prove that the route through Salt Lake City was passable year round and it was, though it was dangerous and difficult as well. Despite the hazards, the 182 young riders — some as young as 15-year-old William F. (Buffalo Bill) Cody — logged 650,000 miles carrying more than 34,000 pieces of mail in the short time the freight company stayed in business.