Sarah Lewis’s career path started long before she became an assistant professor of art history and African-American studies at Harvard, or held curatorial positions at the Museum of Modern Art and the Tate Modern. 

It began in 1926 with a simple question her grandfather Shadrach Emmanuel Lee asked in a Brooklyn high school history class. “His question was, ‘Where are the African-Americans in this history book?’ ” she said. “And the answer he received was, ‘Well, African-Americans have done nothing to merit inclusion.’ He didn’t take that as a legitimate answer. So he was expelled for his impertinence. And his pride was so wounded that he just never went back.”

Mr. Lee never finished high school but did become a visual artist and pursued a career as a jazz bassist playing with Billy Eckstine, Lionel Hampton, Count Basie and others. To support his family, he also worked as a janitor, including for a time at Temple University in Philadelphia. 

But that high school encounter motivated his granddaughter to become an art historian and explore the relationship of race, identity and imagery in the United States. Last year, Ms. Lewis became only the second professor hired at Harvard to focus on African-American art and also edited the Aperture magazine issue devoted to African-Americans, race and photography. Starting tonight, she will be teaching a three-part course, “Vision and Justice,” at the Brooklyn Public Library, which is modeled on her Harvard courses. 

When Ms. Lewis began teaching on race and photography at Harvard last September, the United States had a black president and almost all pundits expected Hillary Clinton to become the first female president. Ms. Lewis challenged students to explore how photography, art and design formed concepts of racial identity from slavery to today. As the campaign gained in intensity and issues of racial and religious identity came to the fore, she shifted the final classes to address students’ concerns about the tenor and substance of the political debate. ...