One of his first jobs, in 1916, was selling soda pop at the St. Louis Browns' home field, Sportsman's Park, and working as an office boy during his summer vacation.

As a young man, DeWitt studied law at night at Washington University in St. Louis, passed the Missouri Bar exam,[2] and became the first treasurer of the Cardinals.

DeWitt ultimately joined the Browns, the city's underdog American League (AL) team, in November 1936 as minority owner (initially in partnership with majority stockholder Donald Lee Barnes) and general manager.

[3] The Browns were cash-strapped and struggling to survive as the second-ranked team in one of the smallest markets in the big leagues, during The Great Depression.

Meanwhile, Rickey disciple DeWitt managed to use some of his scant resources to strengthen the Browns' farm system and scouting department, signing and developing Vern Stephens, Al Zarilla, and Jack Kramer—all future major league stars.

[5] He also attempted to add depth and unearth hidden talent by trading the Browns' few veteran assets, such as pitcher Bobo Newsom, for second-string players or minor leaguers with other organizations.

They drew as their World Series opponents their formidable tenants at Sportsman's Park, the Cardinals, who had won 105 games to breeze to their third consecutive National League championship.

The Browns' pennant is often downplayed by observers because it occurred during the height of the World War II manpower shortage, when most of the top American League players were in military service.

DeWitt was forced to sell Stephens, Kramer and Zarilla—along with pitcher Ellis Kinder, a future 20-game-winner—to the wealthy Boston Red Sox to keep the team solvent.

But the experiment fizzled; the players performed below expectations and encountered resistance from their manager, Muddy Ruel, and some of their white teammates.

DeWitt and his brother Charlie (1900–1967), the Browns' traveling secretary, bought control of the club from majority owner Richard C. Muckerman in February 1949, but the team's struggles on the field and at the box office continued: they lost 101 and 96 games, and drew an average of 259,000 fans a season, in 1949–1950.

In his 14 months as the Tigers' president, DeWitt participated in three significant trades with swap-happy Cleveland Indians GM Frank Lane during the 1960 season.

The Robinson deal somewhat clouded DeWitt's Cincinnati legacy, although many of the players he had signed or developed became key members of the team's "Big Red Machine" dynasty of the 1970s.

[13] DeWitt's last official post in baseball was as chairman and minority owner of the Chicago White Sox from 1975 to 1981, working with the flamboyant Veeck once again.