Topographical Engineers
In 1838, a separate department known as the U.S. Army's Topographical Engineers was created (not to be confused with the Corps of Engineers with whom they were merged during the Civil War). Lieutenant Simpson was one of the officers transferred to the newly created bureau and assigned as an assistant to Captain W. G. Williams who was in charge of harbor construction on Lake Erie. The following year, he worked on road construction in Florida and then lake surveys in Wisconsin and Ohio. From 1845 to 1847, he was in charge of the harbor of Erie.
Read more about this topic: James H. Simpson