When the earliest Spanish explorers ventured upon New Mexico's eastern plains, they discovered Indians there, mostly Apachean-speaking, who were true "dog nomads." Most people I suspect, have never heard of them. But their way of life makes a beguiling story.

It is generally known that the Spaniards brought the first horses to the Southwest. In the pre-horse era, Indians dwelling on the open plains had only the dog as a beast of burden.

About them, Coronado in 1541 wrote: "They have dogs that they load, which carry their tents and poles and belongings." And he made reference to Moorish-style packsaddles with girths.

Gaspar Castaño de Sosa, who entered New Mexico in 1590 by ascending the Pecos River, bumped into migrating Apaches whose dogs were bearing all their worldly goods.

"That was a thing new to us," he wrote in astonishment, "never before seen." One of the dogs, he observed, had two heavy hides tied to his back, and a breast collar and rump strap under his tail. They prevented the load from slipping.

Larger dogs serving as draft animals pulled a simple device, the travois. It consisted of two long poles that joined on one end at the animal's shoulders, while butt ends dragged on the ground.

Halfway down the poles was a platform of rawhide netting. Upon it, bundles up to 75 pounds could be transported. Pack dogs, bearing burdens on their backs, carried no more than 50 pounds.

In 1599, Vicente de Zaldívar, hunting buffalo on the plains for the Oñate colony, watched the packing procedure. It was done by Indian women who seized the dog and held its head between their knees in a vice-like grip. Efficiently, they secured the load to the packsaddle.

Dog handling among the nomads was women's work. Their skills were most in evidence when a large camp decided to move.

Each family might use between 10 and 20 dogs to transport tent poles and covers, quantities of dried meat, and personal possessions. A dog train on the move was spectacle to behold.

Zaldívar viewing one thought it laughable, the way the animals snarled and snapped at one another and the women ran among them to break up fights.

Sometimes, tired or overloaded dogs would lay down during the march and howl. Their owners promptly waded in with sticks or clubs to set them back in motion.

Occasionally, an entire train would erupt in a mass dogfight, requiring intervention by all the female population to end it. The men stood by on the fringes, observing "the entertainment" but offering no assistance, that being beneath them.

One story has it that a couple of loaded dogs spotted an antelope and eagerly broke ranks and gave chase. Within moments, every dog in the cavalcade had joined the leaders, leaving spilled packs and broken travois scattered across the wide plain.

When Spanish expeditions initially encountered the dog nomads, it was clear that the Apaches already had a well-established trade alliance with the Pueblo Indians.

Seasonally, they would pack up their dogs with jerky and buffalo hides and, either in small groups or large bands, pick up trails that led into the Rio Grande Valley.

From the Tewa province in the north to the Piro district in the Socorro Valley, the nomads streamed in accompanied by their picturesque dog trains. The pueblos gladly awaited them, ready to barter with their corn, squash, wild tobacco and woven cotton blankets.

The introduction of the horse into the Southwest produced sweeping changes in the traditional pedestrian culture of the plains people. They obtained the new animals by theft from New Mexican settlements and later by capturing "wild" horses whose ancestors had escaped and founded free-roaming herds.

The Apaches and other tribes learned to breed, care for, and use horses. Now they could gravel farther and faster on horseback, and transport larger and heavier loads.

The old dog travois was enlarged and adapted to the horse. That allowed the original small, light tents to give way to full-size tepees with their long and cumbersome poles and weighty skin covers.

We might assume that use of pack dogs disappeared, but not so. They continued alongside pack horses, while bearing small loads whose contents could be handily retrieved when needed on the trail.

For example, warriors of plains tribes often went on horse raids, traveling afoot to more easily escape notice and intending to ride stolen animals on their return.

A common practice was to carry extra moccasins and spare food and ammunition on dogs. That was a rare instance when men proved willing to manage those animals.

Famed western artist George Catlin painted a scene that he had witnessed on the Southern Plains in 1834. In the center of a traveling village of Comanches, loaded dogs are engaged in a tumultuous affray. Desperate women wielding sticks are seen in their midst attempting to restore order. Horses dragging travois, unperturbed, pass serenely in the background!

The last report of a working pack dog or two dates from 1870. Then they were gone, to be remembered only by history.

Historian Marc Simmons is author of numerous books on New Mexico and the Southwest. His column appears Saturdays.