This work belongs to Indiana's 1962 Polygon series, small paintings featuring a numeral from 3 to 12 placed inside a polygon of the corresponding number of sides (i.e. 3-Triangle, 4-Square, etc.). The series features extensive wordplay, with references that are playful, personal, literary, and alliterative. The serial nature of these works and their small scale allowed Indiana to experiment with new and bold color combinations previously unseen in his work.
In Polygon: Pentagon the word Pentagon appears at the bottom of the composition in white and again around the circle, which reads “Particci Pentagon.” For an American, the first association of the word “Pentagon” would be with the headquarters of the Department of Defense in Washington, D.C., which explains the predominant colors of the work being red, white, and blue.
Indiana, however, also brought personal associations to the term, as Particci was the name of his cat. Indiana often detailed Particci’s antics in his journals, and he would later appear alongside Indiana in Andy Warhol's 1964 film Eat.