Pacific Railroad Surveys

The Pacific Railroad Surveys (1853–1855) consisted of a series of explorations of the American West to find possible routes for a transcontinental railroad across North America. The expeditions included surveyors, scientists, and artists and resulted in an immense body of data covering at least on the American West. "These volumes... constitute probably the most important single contemporary source of knowledge on Western geography and history and their value is greatly enhanced by the inclusion of many beautiful plates in color of scenery, native inhabitants, fauna and flora of the Western country." Published by the United States War Department from 1855 to 1860, the surveys contained significant material on natural history, including many illustrations of reptiles, amphibians, birds, and mammals. In addition to describing the route, these surveys also reported on the geology, zoology, botany, paleontology of the land as well as provided ethnographic descriptions of the Native peoples encountered during the surveys.
Background.
Starting in the late 18th and early 19th centuries, many Americans began a westward migration that would come to greatly influence the development of American history. However, water travel remained the most common and most efficient form of transit available. Soon, the development of the steam engine became an invaluable contribution to this westward expansion. As railroads gained popularity in the eastern United States during the 1830s, Americans felt an increased incentive to expand this new technology to the western frontier.
Beginning in the 1840s, several government sponsored expeditions hoped to find potential railroad routes across the west. However, no consensus route emerged due to the selfish economic motives of rival companies. In addition, cities and states competed for the route and terminus so no consensus was reached. Brigham Young, President of LDS Church, wrote, "We never went through the canyons or worked our way over the dividing ridges without asking where the rails could be laid." On March 3, 1853, Congress appropriated $150,000 and authorized Secretary of War Jefferson Davis “to Ascertain the Most Practical and Economical Route for a Railroad From the Mississippi River to the Pacific Ocean.” Davis ordered Brevet Captain George B. McClellan and the Corps of Topographical Engineers (TOPOGS), a division in the United States Army established to “discover, open up, and make accessible the American West,” to fulfill this obligation.
The most important concern for the United States Congress involved the location of where to build the railroad. With government involvement, lobbyists attempted to influence the selected locations because of the important social, political, and economic consequences. In addition, a transcontinental railroad would become a very costly endeavor. In fact, “Even the least expensive proposed routes would equal the federal budget for one year.” Despite these obstacles, a developing urgency clearly indicated the need for a transcontinental railroad. On August 16, 1856, Mr. Denver of the House Select Committee on the Pacific Railroad and Telegraph reported that:
"the necessity that exists for constructing lines of railroad and telegraphic communication between the Atlantic and Pacific coasts of this continent is no longer a question for argument; it is conceded by every one."
Five surveys.
Five surveys were conducted.
From surveys to construction.
Although the Pacific Railroad Surveys (1853–1855) provided valuable information regarding the possible routes for the transcontinental railroad, they were not compelling enough to lead directly to construction. Three important trends also influenced Congress’ final decision. First, the California Gold Rush and the discovery of silver in Nevada led to a dramatic increase in population in the west. Second, the secession of the South from the Union during the beginnings of the American Civil War discounted southern politicians from interfering with a plan to build a northern or central route. Third, a growing population of railroad specialists allowed Congress several options to consider the most efficient and cost effective route to build a transcontinental railroad. 
In particular, railroad engineer Theodore Judah, on 1 January 1857 in Washington DC, published "A practical plan for building The Pacific Railroad", in which he outlined the general plan and argued for the need to do a detailed instrumental survey of a specific selected route for the railroad, not a general reconnaissance of several possible routes that had been done in the Pacific Railroad Surveys. After finding in Fall 1860 a practical trans-Sierra route from Sacramento over Donner Pass into the Great Basin of Nevada and after finding investors to incorporate the Central Pacific Railroad in June 1861, Judah was sent in October 1861 to Washington DC to lobby for the Pacific Railway bill to aid in the construction of the first transcontinental railroad along his trans-Sierra route.
In 1862, Congress passed the Pacific Railway Act. The newly chartered Union Pacific Railroad Company would build continuous railroad and telegraph lines west from the Eastern shores of the Missouri River at Council Bluffs, Iowa (opposite Omaha, Nebraska) which would meet railroad and telegraph lines build east by the Central Pacific Railroad from the navigable waters of the Sacramento River in Sacramento, California. On May 10, 1869, the two rail lines joined with an honorary Golden Spike at Promontory Summit, Utah, after making a combined of railroad track.
Natural history studies.
Leading naturalists were attached to all the survey parties: 
Most of these men also served as the medical doctors for their exploring parties, and most were expert in only one or two areas of natural history. With limited time and expertise, their main charge was simply collection and preparation of plants and animals to be shipped back east for further study. They collected everything: plants, mammals, fish, insects, birds, mollusks, snakes, lizards, and turtles, both common and rare. This approach was described by geologist William P. Blake, who accompanied Lt. Parke's expedition:
The collections in this department of science were not restricted to what was new or undescribed, as I considered it quite as interesting to know that the flora of this region were the same as those common to other parts of the country, or that they were different. It was, therefore, established as a rule to collect everything; it being as easy at the conclusion of the survey to reject what was superfluous, as it would be difficult to replace what was wanting.Plants and animals were preserved as well as could be in the expeditions' camps, and shipped overland back to the Smithsonian Institution and other centers of expertise for evaluation. This trip often required months of rugged travel, and not all the collections survived. Heermann, in a letter of transmittal to Lt. Parke, commented on these difficulties: "Of the reptiles, in which these countries are very rich, I had succeeded in forming quite a handsome collection, but unfortunately the cans in which they were contained became leaky, and possessing neither the means to correct this mishap, nor the alcohol to supply that wasted, they were all lost with the exception of a few specimens which I preserved in bottles."
Several of the expedition naturalists wrote reports on their areas of expertise which were included in the War Department's report to Congress. For example, Heermann wrote the report on birds, and Hallowell wrote the report on reptiles for Lt. Parke's exploration. Other leading naturalists contributed to the War Department's report by describing the collections returned from the exploring parties. These included Professor Asa Gray, Dr. John L. LeConte, William Cooper, Dr. Charles Girard, William G. Binney, and Dr. John S. Newberry. Most important of these was Spencer Fullerton Baird, who was at the time assistant secretary of the Smithsonian Institution. Baird not only wrote several sections of the report to Congress, but was responsible for many of the natural history illustrations. For example, the bird skins collected by the exploring parties were shipped to him. He had Smithsonian Institution artists produce engravings of the birds as they would appear in life, which were hand-tinted and included in the final report.