STS060-83-041 (3-11 Feb 1994) --- The large city of Monterrey, in northeastern Mexico, was founded at the edge between the Sierra Madre Oriental and the Rio Grande Embayment portion of the Gulf Coastal Plain. This location is analogous to the Fall Line along the United States eastern seaboard, but instead of lying along a stream at the head of navigation, Monterrey lies at the boundary between a well-watered mountain range and a semi-arid plain where irrigation is often necessary for successful agriculture. The mountains themselves are formed from folded limestone and shale beds; to the south of the city, beds are crumpled into tight folds. Around and north of the city, more open folds gradually give way to nearly flat-lying beds of the coastal plain. Because of the water and other resources such as shale and limestone to quarry and burn for cement, Monterrey early became a thriving industrial center. It is now one of Mexico's largest cities with a population of approximately 5 million. According to NASA geologists, the STS-60 photography of this area is the best that has been acquired during the past 32 years of space photography by the United States. Monterrey remains an area of high interest for future photography in order to assess the impact of urbanization in this area.