Finely executed Geological Map, centered on Texas and published in conjunction with search for the most practicable route for a railroad line to the Pacific Ocean.
Nice example of William Phipps Blake's geological railroad survey of the region between the Red River to the Rio Grande River. The map depicts from the Rio Grande River and El Paso to the Mississippi River and Baton Rouge and from the Red River and its tributaries to the Gulf of Mexico.
Explored by Captain John Pope, this would become the region traversed by the Southern Pacific.
An 'index of colors' along the left border illustrates the differences between the deposits: granite, limestone, sandstone, gypsum, and others. Copper mines, several mountain ranges, forts, and myriad rivers are labeled.