Probably Hon. John P. Usher

Chicago citation style
War Department. Office of the Chief Signal Officer. (8/1/1866 - 9/18/1947). Probably Hon. John P. Usher. 1860-01-01/1865-12-31. Retrieved from the Digital Public Library of America, http://catalog.archives.gov/id/526825. (Accessed June 22, 2018.)
APA citation style
War Department. Office of the Chief Signal Officer. (8/1/1866 - 9/18/1947), (1860-01-01/1865-12-31) Probably Hon. John P. Usher. Retrieved from the Digital Public Library of America, http://catalog.archives.gov/id/526825
MLA citation style
War Department. Office of the Chief Signal Officer. (8/1/1866 - 9/18/1947). Retrieved from the Digital Public Library of America <http://catalog.archives.gov/id/526825>.
Note: These citations are programmatically generated and may be incomplete.