EXCERPT:  Stephen Budiansky's new book, The Nature of Horses

In a chapter about the evolution of the horse he talks about the evolution of size and speed:

"The usual explanation for these changes, and for the eventual appearance of the single-toed foot in Pliocene horses (beginning 5 million years ago) is that, as grassland animals, these grazing horses were more exposed to predators and had to be able to flee.  The evolution of the diastema may be related to this fact too: a long distance between the front of the mouth and the eyes allows an animal to graze and keep an eye out at the same time.

There is no doubt that larger animals are faster and that the springing hoof allowed for a faster gait.  The almost unbelievable discovery of fossil footprints of three Hipparion horses from the middle Pliocene (3.5 Million Years ago) have provided ample confirmation of the sped and agility of these grasslands-adapted horses.  Although Hipparion still had three toes on each foot, it had already developed the springing foot mechanism;  and in spite of its relatively small size, its overall proportions-leg length relative to body size, for instance- are quite similar to those of modern horses. 

The two side toes in Hipparion species, while able to help balance the foot and even add some to the locomotive effort, were already much reduced in size compared to those of their ancestors, and clearly most of the work was done by the large central toe.  The Hipparion footprints, made in soft lava subsequently covered with volcanic ash, were discovered in Tanzania by Mary Leakey in 1979, along with trails of a number of other mammals, including early hominids. 

The Tennessee Walking horse carries the blood of four distinct living breeds - the Thoroughbred, Standardbred, American Saddlebred, and the Morgan, plus two breeds that are virtually extinct - the Narragansett Pacer and the Canadian Pacer.  While English Thoroughbreds, Morgans, Standardbreds and coach horses may all be found in the background of Tennessee Walking horses, it was the Canadians and Narragansetts who formed the basis for their gaits.   The two earliest strains, or breeds, of horses recognized in North America were the Canadian Pacer, a breed still existing in small numbers in Canada, which evolved from Norman horses brought to Quebec by French settlers; and the now-extinct Narragansett Pacer, which evolved from British Hobbies and Galloways brought to the American Colonies by English settlers.

About 150 years ago in American history, when the hill people of Kentucky, Virginia and Tennessee crossed the Mississippi River to settle the Ozark Mountain regions of Missouri and Arkansas, they took with them their best horses.  The square trotting horses were able to cover the ground, but their gait was uncomfortable, and tiring for both horse and rider within just a few miles.  The "Walking Saddle Horse," or "Plantation Horse" as the Tennessee Walker was called then, would do a running walk, and that was fast and comfortable.  While the bloodlines of the Gray Johns, Copperbottoms, Slashers, Hals, Brooks and Bullett families ran thick and produced a type known as the Tennessee pacer prior to the arrival of Allan F-1 in Middle Tennessee, it was a cross between Allan and the Tennessee Pacer that produced today's Tennessee Walking Horse.  At this time, the most prominent saddle horse was the now-extinct Narragansett Pacer, which originated around Narragansett Bay, in Rhode Island.

To the North in the Canadian Provinces, French mares were crossed with English and Dutch stock, to produce what became known as the Canadian Pacer, a breed which still exists, but in very small numbers in that country. 

Then, the American Colonists began crossing their gaited stock with the English Thoroughbreds.  One famous stallion was Hedgeford, imported in 1832, and his most remembered son was Denmark.

Denmark was bred to a mare of Narragansett background known as the Stevenson mare, from Cockspur bloodlines, and their foal was Gaines Denmark. During his career, Gaines Denmark produced four legendary sons, and in 1908, the American Saddle Horse Breeder's Association named him THE single foundation sire of the Saddle Horse breed. Previous lists had included such horses as Harrison Chief, Tom Hal and Copperbottom.

Understandably, as harness racing became popular with Colonial gentlemen, these horses made their way towards the colonies of Kentucky, Virginia and Tennessee. Inevitably, as frontiers moved south and west, the Narragansett and Canadian Pacers came together. The Canadians went to New England, where they became a part of the foundation of what is now the Morgan breed.

 The Tennessee Walking Horse was derived in Tennessee, primarily from the American Trotting Horse  with the heavy influence of the Morgan Horse and the Canadian Pacer.  The American Trotting Horse is now known as the Standardbred.

The war Between the States occasioned the crossbreeding of the Confederate Pacer and Union Trotters: thus the Southern Plantation Walking Horse or Tennessee Pacer came into being.   Next came the blood of the Thoroughbred, Standardbred, Morgan and the American Saddlebred.  All were fused into one animal in the middle of Tennessee bluegrass region.  The result, over countless years, was the "world's greatest show, pleasure, and trail horse,"- the first breed of the horse to bear a state name - the Tennessee Walking Horse.