Before becoming an executive, he spent two seasons in the major leagues as a catcher. Debuting as a St. Louis Brown in 1905, he hit fairly well in 1906 but was a lousy fielder, a skill more important for the position at the time. Sold to the New York Highlanders the following season, he couldn't hit or field while with the club, with his average dropping below .200. In one game, he gave up 13 stolen bases, which still stands as a record. He left baseball after just one year with New York after injuring his throwing arm.
He spent several years at the University of Michigan as a coach and also earned a law degree. He returned to the big leagues in 1913, as a front office executive with the Browns. He was responsible for signing young George Sisler, one of the players coached by Branch. Rickey became the team's manager for the final 12 games of the season, and managed the team for 2 full seasons afterwards. The Browns were not a great organization and his teams were under .500 both years. He was fired in 1916 when new ownership took over the club.
Rickey served in the military for a few years, then returned to St. Louis in 1919, this time to the Cardinals, to become team president and manager. His 6+ years as a manager were mostly uneventful and he was fired during the 1925 season. Off the field, he was much more successful. Rickey invested in several minor league baseball clubs, and used them to help develop future talent for the major league roster.
Rogers Hornsby replaced Rickey to become a player-manager, and in 1926, his first full year as manager, he led the Cardinals to their first World Series championship. Branch rewarded Hornsby by trading the fiery leader and star second baseman to the New York Giants for Frankie Frisch. Frisch would spend a decade anchoring second for the Cards.
By 1930, Rickey's Cardinals, known as the Gashouse Gang, were the class of the National League. They won 101 games in 1931 and won the World Series in 7 games. The star of the Series that year was rookie Pepper Martin, one of the first Cardinal stars that came from Branch's minor league system. Soon, other minor league graduates joined the team, among them future hall of famers Dizzy Dean and Joe Medwick, and Dizzy Dean's brother Paul. The Deans and Medwick were integral parts of the 1934 Cardinals, who won a third World Series title.
Kennesaw Mountain Landis was concerned that Rickey's minor league system was going to ruin the game of baseball, and he twice released over 70 Cardinal minor leaguers in attempts to stop what he percieved to be a cover-up. Despite Judge Landis' best efforts, Branch's minor league system stayed in existence, and similar systems became adopted by every major league team within a few years.
Rickey continued to develop the Cardinals up until the early 1940's. In his final year, 1942, the Cardinals had their best year in franchise history, winning 106 games and a World Series title. The team was led by a new crop of players developed by the Cardinals, two of which, Enos Slaughter and Stan Musial became hall of famers, and several others, among them future MVP Marty Marion, that were among the best at their position during their times. Even their manager, Billy Southworth, was a product of their farm system.
Rickey was a good friend of Brooklyn GM Larry MacPhail, himself a sound baseball man. MacPhail was drafted into the army to serve in World War II after the 1942 season, and the Dodgers hired Branch Rickey to replace him, ending a tenure of over two decades with the Cardinals.
Branch continued being an innovator in his time with Brooklyn. He was responsible for the first full time spring training facility, in Vero Beach, and encouraged the use of now-commonplace items such as the batting cage, pitching machines, and batting helmets. While with the Dodgers, his son, Branch Jr., was the team's farm director.
But his most memorable acts with the Dodgers involved breaking baseball's color barrier, which had unofficially been in place since the mid-1880's. On October 23, 1945, Branch Rickey signed a pair of Negro Leaguers, among them Jackie Robinson to a contract. Rickey would place Jackie with their International League affiliate in Montreal, the Royals, for the 1946 season. He would be the league's batting champion, and led the Royals to a dominant league championship.
5 days before the start of the 1947 season, Rickey purchased Jackie Robinson's contract from the minor leagues. Amidst much fanfare, Jackie would debut for the Dodgers on April 15, 1947, becoming the first African-American to play in modern major league baseball. Rickey's "Great Experiment", as it was termed, turned out to be a fantastic success. Robinson was baseball's first rookie of the year, and, while he was often jeered by opposing baseball fans, players, and managers, he became extremely popular among the American public. His success became the crowning achievement of Rickey's illustrious career. His Dodgers would make the Series that year, but would lose in 7 games to the New York Yankees.
Branch continued to run the Dodgers until he resigned in 1950, with owner Walter O'Malley more or less forcing him out. He was not out of a job long, as he signed with the Pittsburgh Pirates to become their general manager. Unlike his years with St. Louis with Brooklyn, his tenure with the Pirates was fairly uneventful all around. The Pirates were a stuggling organization that lost 100 games in 3 consecutive years during his tenure, and he stepped down from the team in 1955.
Rickey returned to baseball in 1959, this time as president of a third major league, the Continental League. Major League Baseball was forced to intervene, and made an agreement with Rickey to disband the league in exchange for expansion of the existing leagues.
In addition to his son Branch Jr., who died four years before his father, Branch Rickey's grandson, Branch III, also involved himself in baseball. He is currently president of the Pacific Coast League.