Charles Herbert Klein (October 7, 1904 – March 28, 1958), nicknamed "the Hoosier Hammer" because of his Indiana roots, was an American professional baseball outfielder.

Klein played in Major League Baseball (MLB) for the Philadelphia Phillies (1928–1933, 1936–1939, 1940–1944), Chicago Cubs (1934–1936), and Pittsburgh Pirates (1939).

Within a year, he worked his way up to the Cardinals' farm team in Fort Wayne, which played in the Class B Central League (roughly equivalent to today's Double-A).

However, Baseball Commissioner Kenesaw Mountain Landis discovered that the Cardinals owned a team in Dayton, Ohio, that also played in the Central League with Fort Wayne.

Landis ordered the Cardinals to sell off the Fort Wayne team and give up the rights to its players.

In the middle of the season, the Phillies added a 15-foot screen on top of the short right-field wall of Baker Bowl.

However, William Baker, the Phillies' notoriously miserly owner, defended the addition of the screen, stating, "a number of accidents happen[ing] on Broad street owing to the balls going over the fence and hitting pedestrians, also damaging automobiles, breaking windshields, etc.

"[10] For the remainder of the season, due to the new height of the right field wall, Klein only hit 4 home runs in the 25 games he played at Baker Bowl after August 1st.

In the second game, the Phillies' pitchers walked Ott five straight times, including once with the bases loaded.

"[11] In 1930, Klein enjoyed one of the best offensive years in baseball history, batting .386 with 250 hits and 158 runs scored,[1] all career highs.

He also set career bests and still-standing Phillies records with 59 doubles, 170 runs batted in (RBI), a .687 slugging percentage and 445 total bases.

[15] On July 6, 1933, he became the first Phillies player ever to bat in an All-Star Game after receiving a majority of the fans’ votes.

As good as those numbers were, they were nowhere near what Klein had posted in Philadelphia, leading to claims that he would not have hit nearly as many homers had he not played in notoriously hitter-friendly Baker Bowl.

Klein was known for exploiting the Phillies home park, the Baker Bowl, and its short right field wall.

After never receiving more than 28% on the ballot, a campaign was started to get Klein elected to the Baseball Hall of Fame via the Veterans Committee.

As with another Philadelphia legend from the pre-numbers era of baseball, Grover Cleveland Alexander, the Phillies simply honored Klein with his name and an Old English-style "P" where a retired uniform number would go on the outfield wall of Veterans Stadium.