At first they were foragers, living on what nature provided. At the time of Christ, several groups could be distinguished: In the Colorado River drainage, south of the Grand Canyon, were the Yuman Foragers; in southeastern Arizona and southwestern New Mexico were the Mogollon people; in the Four Corners area (where the states of Utah, Colorado, Arizona, and New Mexico meet) and in the Rio Grande Valley of New Mexico was a complex of cave sites that evidenced a forager type of culture. But, as man always aspires to rise above his environment, the Indian slowly and painfully learned to make tools, developed new techniques, and finally made the great step upward; he domesticated plants. Agriculture, based primarily on the growing of corn, came to the Four Corners before the Christian era. Gradually, out of the primitive foragers, there developed across the Southwest a complex pattern of agricultural societies; peaceful farmers intent upon harvesting the utmost from a harsh land. In Arizona, the Hohokam peoples created a culture based upon irrigation. In the valleys of the upper Gila and Mimbres rivers of southwestern New Mexico, several branches of the Mogollon culture grew and prospered. In the Four Corners area and in the upper Rio Grande Valley, the Mesa Verde, the Gran Chaco, and later the Rio Grande branches developed, at first in the cliffs of the high country, then in open villages along the main tributaries of the Rio Grande. That there were numerous and varied cultures is attested to by the ruins one finds scattered throughout the Southwest. Along now dry arroyos, on buttes overlooking rivers or dry river beds, among cliffs in the mountain fastnesses and in caves wherever they appear, there are thousands of sites whose people and history are lost in antiquity. [Illustration: Prehistoric Indian cliff dwelling] And these people were builders. They lived in caves at first, then in crude pit houses. Finally they moved above the ground and evolved building techniques and styles of architecture that stood the ravages of time and still serve the people of the Southwest. In the city of Santa Fe, the Palace of the Governors was built upon the ruins of an Indian pueblo (village), the name of which has disappeared even from tradition, and its massive walls of puddled adobe, laid down before the art of making bricks was introduced by the Spanish, may be seen under glass in some of the rooms of the Palace at the present time. Perhaps most spectacular are the great houses of Chaco Canyon, some of which must have sheltered from one to two thousand people each, and which as achievements in building, both from the standpoint of durability and graceful construction, rival the structures of the historic valleys and plateaus of the ancient eastern world.