Henderson founded Pushcart Press in a studio apartment in Yonkers, N.Y., in 1972 while also working as an editor at Doubleday. Pushcart's first and perhaps best-known book was The Publish It Yourself Handbook, a collection of essays from writers and authors about self-publishing and self-published works that Henderson published in 1973. In 1976,
Henderson co-founded The Pushcart Prize Anthology, an annual collection of the best work from small presses around the country. And in 1983, Pushcart created the Editor's Book Award series, which publishes manuscripts that were championed by editors but ultimately rejected by mainstream publishers.