This is the text I wrote for the Online Nevada Encyclopedia on this subject:

In 1856, the U.S. Army experimented with the importation of Middle-Eastern Dromedary (one hump) camels. Lt. Edward F. Beale maintained the animals could haul materials for the military in the arid West. They could carry more than horse or mules, and they had a legendary ability to survive without much water. Beale and roughly thirty camels crossed the Colorado River into present-day southern Nevada in 1857, but his experiment eventually failed, and the army sold what stock survived.

There were other attempts at importing camels including the 1861 introduction into Nevada of nine Asian Bactrian (two-humped) camels. Three years later, Sam McLeneghan purchased ten of the Army's Dromedaries for hauling supplies in the territory. Camels brought salt to mills in both Virginia City and Austin.

The animals generally proved effective, but operators had to avoid paths with sharp rocks, and they found that camels frightened horses. In 1875, the Nevada legislature prohibited camels on public highways to safeguard horse traffic. This effectively ended the commercial use of camels.

Operators set many camels free while selling others to circuses. For decades, various people throughout the West reported seeing the wandering beasts throughout Nevada and the southwest. Although some of the initial accounts may have been based on reality, these stories eventually became part of western folklore.

Camels later assumed a different role in Nevada history and culture. In 1959, the revived Territorial Enterprise reported the results of a fictional camel race held in Virginia City. To the delight of residents, the San Francisco Chronicle reported the event as fact. The following year, actor-director John Houston, in northern Nevada for the filming of The Misfits, heard of the contest and became determined to ride in the "second annual" camel race. Virginia City held an actual competition, Houston won, and the annual camel races grew into a tradition celebrated to this day.

Not quite my area of expertise but I do know that at least one Ottoman was hired by the US Army to help develop their camel program. His name was Hadji Ali and he went by Hi Jolly in America. I think by the Civil War, the program had basically fluttered out.

In 1855 under then Sec. Of War Jefferson Davis (later to be President of the Confederacy) sent Army Quartermaster Major Henry Wayne to the middle-east to requisition camels for testing in the Southwest United States. Upon his return he delievered 34 camels to Texas where they were used in Army caravans across the region.

The Civik War took place a few years later, and the entire endeavour was scrapped. Most of the camels were sold off as excess equipment, though some reportedly escaped into the wild. There were reports as late as the 1930s of wild camels in Texas, but nothing since.

Probably one of the leading reasons camels weren't adopted for regular service has to do with their ability to spook horses, who will become paniced by the smell of them. Add in that camels generally have a crappy disposition, and it makes them less and less worth it.