Harkness was born in Harlem. Before playing in the professional leagues, the 6'3" Harkness was a star at DeWitt Clinton High School and Loyola University Chicago. At Loyola, he served as captain of the team that made a run through the 1963 NCAA Tournament to win the national championship. In the first round of the tournament, Loyola defeated Tennessee Tech by 111–42, which as of 2020 remains the largest margin of victory in an NCAA Tournamentgame. In the second round, Loyola faced Mississippi State in a historic match now known as the Game of Change. Facing Loyola's lineup with four black starters, Mississippi State defied segregationists by participating, breaking an unwritten law against Mississippi teams competing against teams with black players. Harkness was enshrined in history as he shook hands Joe Dan Gold, the white captain of Mississippi State, prior to tip-off. In a 2013 interview, Harkness told NPR of the handshake: "The flashbulbs just went off unbelievably, and at that time, boy, I knew that this was more than just a game. This was history being made." Loyola beat Mississippi State, then sailed past Illinois and Duke to reach the tournament final. Loyola then upset the Cincinnati Bearcats in overtime to win the 1963 NCAA Basketball Championship. Harkness and the other four Loyola starters played the entire game, without substitution. He then advanced to the pros after being drafted by the New York Knicks in the 2nd round of the 1963 NBA draft. Harkness played one season with the NBA's New York Knicks. He then played two seasons with the ABA's Indiana Pacers. Though his professional career was relatively short, he left his mark in the record books on November 13, 1967, when he hit a game-winning buzzer beater to lead the Pacers past the Dallas Chaparrals. This is still the longest shot ever made in any American professional basketball game.
Life after basketball
Harkness became the first African-American salesman for Quaker Oats. In 1970, Harkness became the first African-American fundraiser in Indianapolis, working for the United Way of Greater Indianapolis. He was Indianapolis' first African-American sportscaster at WTHR in the mid to late 1970s. He has also devoted much of his time to civil rights issues. He worked with the Southern Christian Leadership Conference in the early 1970s, and he currently serves as executive director of the Indianapolis chapter of 100 Black Men, a national organization dedicated to supporting and training young African American males.