Robert Indiana kept a series of illustrated journals during the late 1950s and 1960s, in which he discusses the development of his work as well as his daily life on Coenties Slip.

In his first entry on this journal page, dated August 3, 1960, Indiana discusses Moon Machine. To the left of a sketch of the work he writes "mount 8 wheels today, some of which require remounting for alignment purposes. Each turns independently of each other, with [the] exception of one of two inciting its adjacent neighbor into rotation." To the right of the sketch, in a note added at a later date, he records that the title was later shortened to Moon, and that the work was part of an assemblage show (The Art of Assemblage) at the Museum of Modern Art, which acquired the work, and at museums in Dallas and San Francisco.

He continued working on Moon the following day, recording in his entry for August 4, 1960, that he incised and gessoed a 6 x 5-inch lunar symbol for Jupiter on the left side of the construction, and added an "I" and "60 USA" on the bottom left and right respectively.