William Emory was an 1831 graduate of the U.S. Military Academy at West Point. When the Mexican War broke out, he was assigned as chief engineer officer to General Stephen Kearny, whose army traversed largely unknown territories in the West. The U.S. War Department would later print 10,000 copies of Emory's Notes of a Military Reconnaissance, which made a significant contribution to understanding the geography and topography of the Southwest.
A tiny village on the Rio Grande River in northern New Mexico became the training center for the first American hydrographers and provided the first stream-gauging operations of the U.S. Geological Survey. To plan any water system, it is necessary to know the amount of water flowing in the stream or river at all times - including low, normal, and flood conditions.