New Mexico was a frontier to the wilderness, for Europeans, for almost three hundred years. No other frontier history in the area of what is now the United States can support such continuity, or even come close. It was the outside edge of the northern borderlands of New Spain, that later became the northern borderlands of Mexico. It was the western rim of the world for the French explorers and fur traders in the Mississippi valley and for the English who followed them there. It was lastly the frontier for the newly minted Americans who came with the opening of the nineteenth century to Missouri, the sill of the great plains, across which lay fabled Santa Fe, for Santa Fe, New Mexico's capital, was in effect another name for the entire province. The route between the Missouri River and New Mexico that eventually became known as the Santa Fe Trail was a road not for would-be settlers but for exploration, trade, adventure, and as such it was more an extension of the frontier itself than a road leading to a frontier. And it remained so throughout a very long sweep of time, from before -- from long before -- the founding of Santa Fe or the earliest Spanish exploration in the Southwest. Quivira provides a closely written synthesis of Spanish exploration eastward from New Mexico and French exploration westward from Louisiana and "the Illinois" in the sixteenth, seventeenth, and eighteenth centuries. Archaeological and ethnological evidence is presented to show that the country between these regions had been a frontier between east and west from time immemorial. William Brandon ably demonstrates that European efforts to penetrate this ancient frontier were predominately motivated by illusion -- misconceptions or outright fictions dealing with supposed riches someplace ahead. Brandon explores the question of whether the pursuit of illusion is a distinctive activity of all people or only of certain societies who possess an overwhelming interest in gain, profit, and money. Brandon concludes by asking whether or not a world established by Europe in American continues this bent for self-delusion.