Project Horizon was a 1959 study to determine the feasibility of constructing a scientific / military base on the Moon. During this time, the U.S. Army, Navy, and Air Force had responsibility for the U.S. space program.
On 8 June, 1959, a group at the Army Ballistic Missile Agency (ABMA) produced for the U.S. Department of the Army a report entitled Project Horizon, A U.S. Army Study for the Establishment of a Lunar Military Outpost. Some reasons cited were military and scientific advantages over other nations. The program would also assure demand for the rockets ABMA was designing.
According to the documents:
“The lunar outpost is required to develop and protect potential United States interests on the moon; to develop techniques in moon-based surveillance of the earth and space, in communications relay, and in operations on the surface of the moon; to serve as a base for exploration of the moon, for further exploration into space and for military operations on the moon if required; and to support scientific investigations on the moon.”
Below you will find the documents obtained about the plans.