Keep two general concepts in mind as you begin your study of Castolon, a small trading and farming community in far southwest Texas. First, although international boundaries sometimes correspond to natural features we can see--the U.S.-Mexican boundary does follow part of the course of the Rio Grande--borders themselves are not a visible part of the landscape. They exist because humans have created that idea, and they can change over time.

Second, trends and new technology do not always appear in all places at the same time. For example, while many Americans were driving automobiles and having milk delivered each morning to their houses, people in West Texas still traveled largely by horse or horse-drawn wagon and depended on their gardens, fields, and livestock for most of their food.

West Texas is arid, sparsely vegetated, and shows a great deal of topographic variation. The buildings in the Castolon Historic District sit on a mesa about 1,900 feet above sea level and just above the flood plain of the Rio Grande. About two miles away from the La Harmonia Store, a line of huge limestone cliffs--the Sierra Ponce--fill the southern horizon. To the north lies a single, flat-topped peak called Cerro Castellan and, beyond that, the Chisos Mountains. Average rainfall in the Castolon area is about eight inches each year. The soil is colorful, and woody shrubs and grasses grow in occasional clumps. The Rio Grande, about one-half mile away, is a muddy river which many people could wade across most of the year. During flood periods, however, the river roars past and has even flooded the lower areas where people farmed and lived.