As a historian, Clarke wrote and edited numerous books on Pan-Africanism, including African People at the Crossroads published in April 1992. His historical works are widely used in history classes and African-American studies at colleges and universities.
During his career, Clarke edited or wrote 27 books. His edited work included the classic American Negro Short Stories in 1966. He also wrote more than 200 short stories, including The Boy Who Painted Christ Black.
Originally his name was spelled John Henry Clark. However, he added the “e” onto his family name and changed the spelling of his middle name “Henry” to “Henrik” after the Scandinavian rebel playwright Henrik Ibsen.
During the Black Power movement in the 1960s, Clarke advocated for studies on the African-American experience and the place of Africans in world history. He challenged the views of academic historians and helped shift the manner in which African history was studied and taught.
As a scholar, Clarke was devoted to redressing what he saw as a racist suppression and distortion of African history by traditional scholars.
In 1968, along with the Black Caucus of the African Studies Association, Clarke founded the African Heritage Studies Association in New York, which expanded nationally over time.
In 1969, he was appointed the founding chairman of the Black and Puerto Rican Studies Department at Hunter College in New York City.
Clarke was an adviser and personal friend to both Kwame Nkrumah and Malcolm X with whom he was instrumental in drafting the charter for the Organization of Afro-American Unity founded in New York City in 1964.
“I think every person that calls themselves a leader, a preacher, a policy maker of any kind should ask and answer the question in his own life time, how will my people stay on this earth? How will they be educated? How will they be schooled? How will they be housed? And how will they be defended? The answer to these questions will create the concept of enduring nationhood because it creates the concept of enduring responsibility. I am saying whatever the solution is, either we are in charge of our own destiny or we are not in charge. On that point we got to be clear, you either free or you a slave.” – Breaking the Chains of Slavery Lecture Series, 1994
“History is a clock that people use to tell their political and cultural time of day. It is also a compass that people use to find themselves on the map of human geography. History tells a people where they have been and what they have been, where they are and what they are. Most important, history tells a people where they still must go, what they still must be. The relationship of history to the people is the same as the relationship of a mother to her child.” – A Great and Mighty Walk, 1996
“My main point here is that if you are the child of God and God is a part of you, then in your imagination God suppose to look like you. And when you accept a picture of the deity assigned to you by another people, you become the spiritual prisoners of that other people.” — A Great and Mighty Walk, 1996
“Powerful people cannot afford to educate the people they oppress … because once you are truly educated, you will not ASK for power you will TAKE it.” – Africans at the Crossroads: African World Revolution, 1992
“The people and the cultures of what is known as Africa are older than the word ‘Africa.’ According to most records, old and new, Africans are the oldest people on the face of the earth. The people now called Africans not only influenced the Greeks and the Romans, they influenced the early world before there was a place called Europe.” — Why Africana History? January 1987
“Africans in the United States must remember that the slave ships brought no West Indians, no Caribbeans, no Jamaicans or Trinidadians or Barbadians to this hemisphere. The slave ships brought only African people and most of us took the semblance of nationality from the places where slave ships dropped us off.” – The Impact of Marcus Garvey, 1960s