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.

Indiana's journal page for January 30, 1959, includes a sketch of Source I in a vertical orientation. The artist records that artist Robert Dash persuaded him that it would be a better painting hung this way, "letting the blue thrust to the left and the egg push right." He notes that he himself had considered hanging it vertically, but rejected it because it too much resembled one of Ellsworth Kelly's series of works. Indiana also writes that "another disturbing thing about this position is that the image becomes to look like half a Greek mask, but perhaps this is better than the underwater diver's helmet that Bob [Dash] saw in it otherwise."