After resigning from being a principal he started a construction company to build homes for poor black people.
While at Howard he also studied with Sterling Allen Brown, E. Franklin Frazier, Alain LeRoy Locke, Charles H. Wesley, and Ralph Bunche.
In 1945, Willis began graduate study at Columbia University in New York City in political science.
[7] In 1949, Willis was awarded the John Hay Whitney Opportunity Fellowship to fund his research dissertation at Columbia, university.
The dissertation focused on documenting Cherokee American society and culture, sociocultural change, assimilation, and adaptation in a colonial environment using a historical approach in anthropology.
His classmates while at Columbia University became noted in the field of anthropology such as; Eric Wolf, Sidney Mintz, Morton Fried, Robert F. Murphy, Elliott P. Skinner, and Marvin Harris.
During this time he pursued his research interest in early colonial Southeastern North America publishing two articles on Indian culture patterns and Black-Indian-White relations.
In addition to examining the standard historical treatises, he looked for "ethnographic facts found now and then in routine documents written by busy officials and semi-literate traders" and compared these facts with the extended descriptions of more sophisticated authors (Willis 1957: 125).
The scholarship was enlivened by the personal interest Willis took in the five groups he studied: Cherokee, Choctaw, Chicasaw, Creeks and Seminoles.
He published two articles that focused on ethnohistorical issues in Indian culture patterns, and Black-Indian-White relations.
[8] Chicasaw, In 1964 Willis returned to Dallas, Texas after spending many years in New York City.
He accepted a teaching position at Bishop College in Dallas, Texas in the Division of Social Sciences, and in the Department of Sociology.
In 1972, he resigned from Southern Methodist University in protest to racist treatment from the faculty in the Department of Anthropology.
He corresponded with George M. Foster, Morton Fried, Elliott P. Skinner, Sidney Mintz, Marvin Harris, Dell Hymes, Charles H. Fairbanks, Rayford Logan, and Arthur Fauset.
He is quoted in the letter of recommendation by Morton Fried as "one of the country's authorities on the Colonial period in the Southeastern United States."
Fried also stated that Willis had "an unusually acute grasp of the historical problems (of this area) in terms of the triangle constituted by Indians, Negroes and the European settlers."
In Willis' 1957 article "The Nation of Bread" his research approach combined the historical method and the Boasian anthropology.
He did not explicitly refer to the slave trade, slavery, segregation, imperialism, discrimination, exploitation, lynching.