He began working in the photography world as a college intern at Light Gallery in 1973 where he hung Stephen Shore’s first solo show.
[6] While attending the University of Arizona MacGill served as a curator at the Center for Creative Photography.
[9] In 1999 the gallery sold Man Ray's Glass Tears (1930–33) for $1.3 million, at the time the highest price ever paid for a photograph.
[11] In 2006 MacGill set a new record when he bought Edward Steichen’s The Pond—Moonlight for $2.9 million on behalf of a private buyer.
[12] In 2019 MacGill established a partnership with RadicalMedia to develop a streaming platform focused on the history of photography.