EXPANSION OF COLONIAL SPANISH HORSES FROM SANTA FE, AND MIXING WITH FRENCH AND ENGLISH HORSES
There were once herds of Mustangs on the western plains so numerous as to be beyond count. Stephen Austin’s 1829 maps of eastern Téjas bear the notation “immense herds of wild horses.” As the first three maps show, the Mustang population explosion came from Santa Fe, a Spanish-Mexican colony in what is now New Mexico. As the maps show, purple zones of mixing developed east of the Mississippi but the geographic scale was much smaller. By 1790, French exploration westward from Montreal and southward down the Mississippi, and American expeditions heading northwestward to the headwaters of the Missouri created the initial Plains Cayuse population ( purple zone north of St. Louis and west of the Mississippi). By 1870, American immigration to Spanish-Mexican Téjas and California had shifted the purple zone westward and southward. Despite the fact that Plains Cayuses once mounted many Indian tribes and most cowboys and vaqueros, the type is rarely seen today.