The Trail's Predecessors
Texas longhorns were descendants of cattle brought over by the Spanish. English cattle may also have been bred into the line -- I've seen arguments both for and against, and so far have found the arguments against to make more sense. (Show me DNA testing and I'll reconsider.)
Whatever the genetic background, the fact remains that the longhorns were left alone to survive in the wilds of northern Mexico and southern Texas while the men went away to fight each other in the Civil War. Nature converted the once domesticated animal into a lean and hardy breed, fully capable of defending itself against most predators with its long horns and sharp hooves.
The end result was a breed of cattle, resistant also to disease and drought, that flourished until it numbered in the millions. As the buffalo were all but hunted out of existence, their place (in the southern regions, anyway) was taken over by the longhorns. Yet within half a century, the Texas longhorns also were nearly extinct as a species.
At the end of the War Between the States, a seemingly endless supply of longhorns existed. Harry Sinclair Drago writes in Wild, Woolly & Wicked that they were considered next to worthless in Texas. Thousands were killed for the tallow and hides -- a good cowhide might bring as much as $3. Markets for the entire animal were rare -- primarily New Orleans and Mobile, which couldn't handle them in any large quantities.
Small herds of cattle were driven through the Indian Nations (a part of what later became the state of Oklahoma) to markets in Missouri and Illinois, when possible, during the war. After the war, if the cattlemen could get their product to Chicago, a market was waiting for them there -- paying as much as $35 to $40 a head. This first trail was called the Shawnee Trail, and later was known as the Texas Trail or the Texas Road.
The year was 1866. The war was over, but bitter emotions lingered. And not just because of the war.
The Indian Nations had been settled by Native Americans who had been forced to move there while under the presidency of Andrew Jackson. Known as the Civilized Tribes, these formerly Eastern residents were interested in starting new lives -- and weren't that thrilled to have Texas cattle trampling their crops and grazing pastures intended for domestic cattle.
Then, if the cattlemen made it to Kansas or Missouri with their herds intact, they had to deal with roving bands of ex-soldiers who called themselves Jayhawkers or red-legs, and who enjoyed murdering Texans.
The cattlemen also had to deal with unhappy farmers and ranchers, prohibitive laws and uncooperative weather.
David Dary, in his book Cowboy Culture -- A Saga of Five Centuries, says 260,000 head of cattle headed toward Kansas and Missouri that first spring and summer, but only about half reached their destinations.