He subsequently served in the Infantry of the United States Army, and rose to the rank of first lieutenant by the time he received an Honorable Discharge.

[1][3] Harris began a career in publishing at Doubleday in the mid-1950s, a time when (as The New York Times observed) "the prevailing notion in the book business was that, with few exceptions, writing by black authors or aimed at black readers belonged to a niche market that was at worst inconsequential and at best narrow and unprofitable.

At Doubleday, he launched the Zenith Book Series, which focused on African-American history for elementary and high school students, and published titles by authors including John Hope Franklin and Rayford Logan.

[1] In 1967, Harris became a senior editor at Random House, where he edited a periodical of black writing entitled Amistad, producing two volumes, in 1970 and 1971.

[1][2] In 1986, Harris founded the independent imprint Amistad Press, specializing in publishing works by and about African Americans.