William J. Keeler (fl. c. 1856 - 1868) was an American civil engineer active during the second half of the 19th century. He is an elusive figure, and little is known of his birth and death dates, places, or early education. He appears in 1856, already working as a civil Engineer in Buffalo with the Erie Canal. In 1862 he received a civilian appointment, and possibly a honorary military rank, to work as an engineer at the Washington Naval Yard. He may also have worked at the Naval Yard in New York (Brooklyn). He was decommissioned in 1864 or 1865, after which he traveled west where he is recorded as an engineer with the Leavenworth, Lawrence and for Gibson Railroad Company. In 1865 he is also mentioned as working with the Union Pacific. In 1866 he was the chief engineer of the Kansas and Nesho Valley Railroad. He appears to have been employed with the department of the Interior Indian Bureau in by 1866 and/or 1867. He released his National Map of The Territory of The United States from the Mississippi River to the Pacific Ocean, one of the most important maps of the American west to appear in the 19th century, 1867. Although based upon government and railroad surveys, the map was a private publication and went through several subsequent editions, reissues, reformatting, and republications. Following the publication of the 2nd edition in 1868, Keeler seems to disappear from all record.