[1] Gammon served in the United States Navy during World War II stationed in Guam from 1944 through 1946.

[3] In 1963, joined Spiral, a collective of Black artists interested in incorporating the concerns of the civil rights movement into their art.

[4] The group met at the artist Romare Bearden's studio and the name Spiral was suggested by Hale Woodruff.

[2] In 1970, Gammon left (BECC) and New York City to take a teaching job at Western Michigan University where he stayed until he retired in 1991 as professor emeritus [3][7] Gammon then moved to Albuquerque, New Mexico, where he became a member of the New Mexico Afro-American Artist Guild and the New Grounds Print Workshop.

[2] Gammon' work was included in the 2015 exhibition We Speak: Black Artists in Philadelphia, 1920s-1970s at the Woodmere Art Museum.