U.S. Army Corps of Topographical Engineers
Although topographical engineers had enjoyed a certain amount of autonomy within the War Department since 1813, there was not an official Corps of Topographical Engineers until 1838. Their primary duty was surveying and reporting topographical features to commanding officers but they also became responsible for assisting the construction of internal improvements and fortifications. The Corps ceased to exist on March 3, 1863, and became part of the broader Corps of Engineers.
Henry P. Beers, "A History of the U.S. Topographical Engineers, 1813-1863," The Military Engineer 34 (1942), 287-91, 348-52.