The Yankees acquire Reggie Jackson by free agency by signing him to a 5-year deal. The American League adds two new teams in Seattle and Toronto. Meanwhile, the 2-time defending world champion Reds are unseated when the Dodgers win the NL West. The Phillies lose Game 4 of the NLCS to the Dodgers. The ALCS is just as dramatic, with the series going to what was then a full 5 games. The Yankees wind up beating the Dodgers in 6 games for their 21st World Series championship behind the famous three-home run game from Reggie Jackson.

The Yankees battle their archrival Red Sox for the AL East title. The race comes down to a memorable one game playoff famous for the Bucky Dent home run that gives the Yankees a lead they don't relinquish. They use that momentum to take down the Royals and Dodgers for a second straight year, and another championship. The NLCS also produces the same result, with the Dodgers beating the Phillies in 4 games.

George Brett, Mike Schmidt, J. R. Richard, Steve Stone and Steve Howe lead their teams through tight divisional races. The Yankees win 103 games, fending off the Orioles who win 100. The Astros and Dodgers battle for the NL West, with the race coming down to a one game playoff. The Astros prevail, beating the Dodgers 7–1. After three losses in the NLCS from 1976–1978, the Phillies reach the World Series after a tight 5-game match with the Astros with the final four games being decided in extra innings. The Royals also capture their first pennant, sweeping the Yankees in the ALCS culminated by George Brett's 3-run home run in Game 3. After over eight decades of disappointmant, the Philles win their first World Series. They defeat the Royals in 6 games.

Hank Aaron breaks Babe Ruth's all-time home run record. The A's dynasty continues as they roll through the AL en route to a World Series matchup with the Dodgers.