When the deepest channel of the Rio Grande became the boundary between the United States and Mexico in 1848, the Army assumed a thankless task: To enforce an invisible boundary in impossible terrain populated—if at all—by people traditionally disposed to crossing the river freely. At times the Army depended on the Texas Rangers. During the Civil War era troops were withdrawn from the Big Bend, and border incidents surged. After the Mexican revolution of 1910 that government lost control of its northern provinces. Bandit gangs plagued both Texas and California. Pancho Villa used border forays to create tension between Mexico and the United States. In 1913, raiding bandit Chico Cano was captured and freed by his gang in an ambush; the next year he killed his Customs Service captor. Cano was photographed with 8th Cavalry Major Roy J. Considine in 1918. Three soldiers and a small boy were killed in a 1916 raid on Glenn Springs led by Navidad Alvarez, a lieutenant of Pancho Villa. The store was looted and houses burned. Livestock raids on ranches sometimes left entire families murdered. Many Texas Rangers were killed in ambush over the years. Smuggling activities abounded. Arms and ammunitions passed into Mexico, and liquor (during prohibition) and silver bullion passed into the United States. [Illustration: Chico Cano and Maj. Roy Considine.] [Illustration: Bandits on horseback.] [Illustration: The Chisos float in morning mist after a rare ice storm.] Where Mountains Float in the Air From a distance the Chisos Mountains don’t look wooded. They seem to be sculpted from naked rock. Even as you begin the drive up Green Gulch you expect to see only buffy grass, century plants, and sotol. But as you pull abreast of Lost Mine Peak the grass is gone from the road’s edge and the shoulders are covered more and more thickly with green, leafy shrubs. Soon you see taller bushes on the open slopes, the evergreen sumac, Texas madrone, cat claw, and common bee-balm, crowned with beautiful deciduous and evergreen leaves. The Chisos Mountains fascinate for so many reasons: their great beauty, their wooded coolness and greenness, the exceptional variety—and rarity—of plant and animal life. Lying close to the border, they encompass an interesting blend of U.S. and Mexican species. But because they stand alone and apart, they support species found nowhere else. And their height creates a temperate environment, a grassed and timbered island in a sea of rock and sand.