I must state that in this Introduction I have abbreviated as much as practicable the titles of books and manuscripts. These are often very long, and it is unnecessary to burden the present text with them, as I shall have to give the full titles in the notes to the Documentary History proper. It may not be out of place to add to the above a brief review of the distribution and location of the various Pueblo groups at the beginning of the sixteenth century, but strictly according to documentary information alone. The location of different villages must be reserved for later treatment, hence as the ranges of the various linguistic groups had no definite boundaries, only the relative position and approximate extent can be given here. Following the course of the Rio Grande to the north from northern Chihuahua, the Mansos were first met, in the vicinity of the present Juarez, Mexico. This was in 1598. Nearly one hundred and forty years later Brigadier Don Pedro de Rivera met them farther north, not far from Las Cruces and Dona Ana, New Mexico. To-day they are again at El Paso del Norte. About San Marcial on the Rio Grande began the villages of the Piros, at present reduced to one small village on the right bank of the Rio Grande below El Paso. The Piros extended in the sixteenth century as far north in the Rio Grande valley as Alamillo at least, and a branch of them had established themselves on the borders of the great eastern plains of New Mexico, southeast of the Manzano. That branch, which has left well-known ruins at Abo, Gran Quivira (Tabira), and other sites in the vicinity, abandoned its home in the seventeenth century, forming the Piro settlement below El Paso, already mentioned. North of the Piros, between a line drawn south of Isleta and the Mesa del Canjelon, the Tiguas occupied a number of villages, mostly on the western bank of the river, and a few Tigua settlements existed also on the margin of the eastern plains beyond the Sierra del Manzano. These outlying Tigua settlements also were abandoned in the seventeenth century, their inhabitants fleeing from the Apaches and retiring to form the Pueblo of Isleta del Sur on the left bank of the Rio Grande in Texas.