The man-and-horse duo survived the brutal Nevada and Utah deserts during the summer months before reaching the Colorado border on Sept. 22. Near the border, Parker left Smokey at a ranch in Utah rather than transport the horse to Parker's hometown, Ann Arbor, Mich., where he joined his parents in October.

Parker is the first person to traverse the northern route—4,883 miles—of the American Discovery Trail from Sacramento to Delaware by horse. He plans to end his travels at his boyhood home in New Haven, Conn.

Parker, 23, who'd never been much of a horseman before, says over the many miles traveled he's bonded with Smokey, who he calls a "kind soul." Smokey, a Tennessee walking horse, has a smooth riding gait, but to ease the horse's journey, Parker says he often walked alongside Smokey.

"I was super careful with Smokey," he says, acknowledging the journey was tough on the animal. He kept his pace relaxed and was aware of his surroundings, especially when traveling through the desert.

"The desert is unforgiving," he says. "If you make a mistake, it can take your life."

To prevent that from happening, Parker's father drove his truck ahead and left hay and 6-gallon water jugs at strategic stops, calling the coordinates in to his son using a Global Positioning System.

"When I'd get into camp, the first thing I'd do is find the water, while Smokey was tearing into the bag of hay eating the whole thing," Parker says.

He says while the physical challenges were immense, knowing he was responsible for his own and his horse's survival was a greater worry. In Nevada, when the trail was unmarked and his maps were no help, he says he relied on intuition and took one day at a time.

"The mental stress is horrible," he says.

The kindness of strangers and his father's assistance helped him to endure. Parker stayed a week at the Baker Ranch, a famous cattle ranch in Nevada, and was later befriended by Ole Lindgren, a rancher in Antimony, Utah.

Parker and Lindgren struck up a quick friendship, and Parker stayed for a month so that Smokey could regain weight.

Before leaving Lindgren's ranch, Parker was loaned a large mule named Danny Boy to carry his 150 pounds of supplies and a cattle-herding dog called Boo to keep him company.

Throughout his trip, Parker says he "met a lot of middle-aged cowgirls who offered me a fresh horse, but I couldn't bear to part with Smokey."

Parker says it took longer for him to bond with Danny Boy and Boo.

The mule was "suspicious of everything" and stubborn. But he is larger than Smokey and much better suited to carry the gear, Parker says. He added that Boo may not continue in spring because of a previous pelvic injury or she may ride on the back of Danny Boy in a milk crate.

And the journey has had several close calls.

Near Sandy Ranch, Utah, Smokey slipped on some shale coming out of a canyon and fell and rolled over Parker. Parker was unhurt, but was worried Smokey had impaled himself on a rock. Luckily neither was hurt, only shaken up, Parker says.

And when Danny Boy reopened a previous foot sore and his ankle became infected, needing two weeks to heal, Parker knew he would miss his time window to cross the Rocky Mountains, so he stopped. The animals are now resting at Lindgren ranch in Antimony, Utah, for the winter. Parker plans to start up again in the spring.