Herds of Camarasaurus, a long-necked herbivore known as a sauropod, travelled almost 200 miles from the plains to the mountains in a bid to find food and water.
The journey would have taken place on a seasonal basis as the 20-tonne, 23-metre long beasts trekked together across vast distances.
The discovery was made by Henry Fricke, head of the geology department at Colorado College, whose work was published in the journal Nature.
His research proves scientists' long-held suspicion that dinosaurs migrated during the dry season, much like modern herbivores including wildebeest and caribou.
"I think it would have been rather slow going, with animals eating as they walked, maybe only going a few kilometres at most as they headed uphill before turning around and heading downhill again," he told The Times.
"Perhaps at this pace juveniles could keep up and could be protected from predators by staying near their huge parents."
By testing isotopes found in the dinosaurs' tooth enamel, Dr Fricke found that Camarasaurus lived in both the plains, where their fossils were found, and the mountains around 200 miles away.
The 145-year-old fossils, which were found in western America, reveal that the herd had been drinking water from high-altitude regions as well as the low-lying desert.
Dr Fricke said their journey from the lowlands to the uplands would have been both noisy and smelly.
"I imagine a lot of noise - rustling of trees as leaves are eaten, and lots of farting: sauropods didn't chew - they did all of their digesting in their gut," he added.
The research team, based in Colorado Springs, plans to test the theory by studying Camarasaurus populations from less arid environments.
They will also carry out tests on fossilised teeth from predatory dinosaurs with the same isotope components, to see if they followed their migrating prey.
Camarasauraus means 'chambered lizard', from the Greek for 'vaulted chamber', referring to the hollow cavities inside the dinosaurs' vertebrae.
The species dates from the Late Jurassic period and fossils are most commonly found in North America.