[3] During the course of his career, Hartnett took part in some of the more memorable events in Major League Baseball history including: being behind the plate for Babe Ruth allegedly calling his shot during the 1932 World Series, Carl Hubbell's strike-out performance in the 1934 All-Star Game and Dizzy Dean's career-altering injury during the 1937 All-Star Game.

[1] However, the greatest moment of Hartnett's career came with one week left in the 1938 season, when he hit a game-winning home run in the bottom of the ninth inning to put the Cubs in first place.

[1] Prior to Johnny Bench, Hartnett was considered the greatest catcher in the history of the National League.

[7] New York Giants manager John McGraw sent scout Jesse Burkett to appraise Hartnett's talent as a player.

[8] Burkett reported back to McGraw that Hartnett's hands were too small for a major league catcher.

[16] Leo Durocher, who played against Hartnett and was a National League manager during Johnny Bench's career, stated that the two catchers had similarly strong throwing arms.

[17] During the major league baseball winter meetings in December 1925, it was rumored Hartnett might be traded to the New York Giants for catcher Frank Snyder and outfielder Irish Meusel; however, Cubs president Bill Veeck Sr., squelched the rumors saying Hartnett would not be traded for anybody.

[2] He also surpassed Jack Clements' major league record of 72 career home runs by a catcher.

[2][14] Hartnett led all National League catchers in putouts, assists, fielding percentage and in baserunners caught stealing.

[27] During an exhibition game against the Chicago White Sox on September 9, 1931, Hartnett was photographed while signing an autograph for gangster Al Capone.

[28] Hartnett replied with a telegram to the Commissioner whimsically stating, "OK, but if you don't want me to have my picture taken with Al Capone, you tell him.

[29] Hartnett was the Cubs' catcher on October 1, in Game 3 of the 1932 World Series against the New York Yankees when Babe Ruth hit his debated "called shot.

[2] At the mid-season point of the 1934 season, Hartnett was hitting for a .336 batting average with 13 home runs to earn the starting catcher's role for the National League team in the 1934 All-Star Game.

[32][33] Hartnett was calling the pitches for Carl Hubbell in the 1934 All-Star Game when the Giants pitcher set a record by striking out future Hall of Fame members Babe Ruth, Lou Gehrig, Jimmie Foxx, Al Simmons, and Joe Cronin in succession.

[40] In the 1937 All-Star Game, pitcher Dizzy Dean kept shaking off Hartnett's signs for a curve ball resulting in a hit by Joe DiMaggio, a home run by Lou Gehrig and finally, a line drive off the bat of Earl Averill that struck Dean on his toe.

[41] Dean had been one of the preeminent pitchers in the National League until the injury to his toe eventually led to the end of his baseball playing career.

[17] Hartnett ended the 1937 season with a career-high .354 batting average and finished second to Joe Medwick in voting for the National League Most Valuable Player Award.

[43][44] On July 20, 1938, Cubs owner Philip K. Wrigley named the 37-year-old Hartnett as the team's player-manager, replacing Charlie Grimm.

With darkness descending on the lightless Wrigley Field and the score tied at 5 runs apiece, the umpires ruled that the ninth inning would be the last to be played.

[51] Hartnett felt the strain of managing a team during the 1939 season as he faced player discontent over the pampering of Dizzy Dean while pitcher Larry French went over his head to complain to owner Philip Wrigley about his lack of pitching assignments.

[65] On January 26, 1955, he was elected to the Baseball Hall of Fame along with Joe DiMaggio, Ted Lyons and Dazzy Vance.

[66] In 1981, Lawrence Ritter and Donald Honig included Hartnett in their book The 100 Greatest Baseball Players of All Time.

In his last job in the majors Hartnett worked as a coach and scout with the Kansas City Athletics for two years in the mid-1960s.