Big Bend National Park "From an elevation of less than 1,800 feet along the Rio Grande to nearly 8,000 feet in the Chisos Mountains, Big Bend includes massive canyons, vast desert expanses, forested mountains, and an ever-changing river. Here you can explore one of the last remaining wild corners of the United States"  NPS Boquillas Crossing Port of Entry per NPS "The Boquillas Crossing Port of Entry is the gateway for those visitors who wish to take advantage of the opportunity to visit Mexico. " "Proper documentation is required to both enter Mexico and re-enter the United States. Mexican immigration in Boquillas requires passports for all travelers of any age. Information about documentation and Boquillas is available from the staff at the Boquillas Crossing Port of Entry, or go to the U.S. Customs website for complete information on what is required: http://getyouhome.gov/html/eng_map.html " Links to Big Bend National Park {NPS - external link} Border Travel and what you may or may not do  {NPS - external link} Advertisement     Forty Days To a Career in Tour Guiding: Tour Guide Educational Course Kindle Edition by William C. McElroy (Author)