The three-point line was first tested at the collegiate level in a 1945 NCAA game between Columbia and Fordham but it was not kept as a rule. At the direction of Abe Saperstein, the American Basketball League became the first basketball league to institute the rule in 1961. Its three-point line was a radius of 25 feet (7.62 meters) from the baskets, except along the sides. The Eastern Professional Basketball League followed in its 1963–64 season.

The three-point shot later became popularized by the American Basketball Association after its introduction in the 1967–68 season. Then commissioner of the ABA George Mikan stated the three-pointer "would give the smaller player a chance to score and open up the defense to make the game more enjoyable for the fans."During the 1970s, the ABA used the three-point shot, along with the slam dunk, as a marketing tool to compete with the National Basketball Association (NBA).

In the 1979–80 season, the NBA adopted the three-point line despite the view of many that it was a gimmick. Chris Ford of the Boston Celtics is widely credited with making the first three-point shot in NBA history on October 12, 1979. Kevin Grevey of the Washington Bullets also made one on the same day.

More Info: en.wikipedia.org