He taught English at Contra Costa College in San Pablo, California and his poems appeared in small magazines. In 1968, he became poet in residence at Lewis & Clark College and taught at Reed College both in Portland, Oregon. Later that year, he entered a manuscript in the U.S. Poetry Prize Competition, submitted by Gwendolyn Brooks. Although he did not win, Brooks calls his work her “clear winner.” Harper said Brooks gave him his career. With Brooks behind him, his book was published by the University of Pittsburgh and reviewed in "Time" in 1970 with a cover essay by Ralph Ellison. In 1996 Brooks presented Harper with the George Kent Poetry Award for Honorable Amendments.