Indiana’s portfolio Numbers consists of ten serigraphs based on his Numbers paintings (1964–65). Each print is accompanied by a poem, written by Robert Creeley and printed both in English and German. The portfolio was published by Editions Domberger and the Galerie Schmela; the latter presented his first European solo exhibition, Robert Indiana: Number Paintings, in March 1966.
Numbers was first exhibited in Documenta 4: Internationale Ausstellung, June 27–October 6, 1968, in Kassel Germany, and in Indiana: Summer in Aspen, a one-day exhibition (August 18) at the Hunter Gallery, Aspen Center of Contemporary Art.
Creeley and Indiana would later collaborate on other projects. In December 1969 Indiana’s childhood drawing Hero was published in an edition of one thousand, accompanied by a poem written by Creeley. And in 1972 Indiana designed the cover for Creeley’s A Day Book, published by Charles Scribner’s Sons, New York.