Several naturalists joined the railroad explorations that moved west from the Mississippi between 1853-1856. Their data was edited by Spencer Fullerton Baird, assistant secretary of the Smithsonian Institution. Baird prepared an ornithology volume in "Reports of Explorations and Surveys to Ascertain the Most Practicable and Economical Route for a Railroad from the Mississippi River to the Pacific Ocean"--one of the most important Federal publications of the 19th century, it contained 738 species of birds and was first book dealing with the whole North American continent The bird section was reissued as a book, "The Birds of North America" in 1860 but was never as popular as works of Wilson or Audubon.
In 1874, Elliot Coues wrote "Field Ornithology." He also founded the American Ornithologists' Union (AOU).
The section of economic ornithology was created in 1885 in the Division of Entomology, USDA. The Bureau of Biological Survey came to be in 1905 and is now US Fish and Wildlife Service, under the Department of Interior.
The 19th Century ended with publication of "Key to North American Birds" by Elliot Coues, which introduced 100's to ornithology. The 20th century has witnessed numerous ornithologists-- you've heard some of their names this semester. Louis Agassiz Fuertes, the best bird painter ever, died 1927, by not looking both ways at a railroad crossing.
Frank M. Chapman wrote the "Handbook of Birds of Eastern North America" inspired the generation before Roger Tory Peterson hit the scene in 1934. Peterson died in 1996.