He signed with the St. Louis Cardinals afterwards and made his major league debut two days before his 27th birthday. He made an immediate impact, not only scoring 9 triples his rookie year, but also leading the league in sacrifice hits with 26. His 1938 season was not as impressive, but he did manage to increase his batting average over .300. Brown had a career year in 1939, not only leading the league in at-bats with 645, but finishing 6th in MVP voting. He began being known as a reliable leadoff hitter and as an infielder that the Cardinals could put anywhere, having played 1936 primarily as a second baseman, 1939 as a shortstop, and 1941 as a third baseman.

After a decent season in 1940, he came back with another great year in 1941, tying a career high in triples with 9, earning a career high batting average with .306, and finishing 4th in MVP voting. This, however, was still not enough to earn an all-star appearance. In 1942 he managed to earn his lone all-star appearance and finish 13th in MVP voting. Despite this and leading the league in at-bats with 606, his batting average dipped to .256, a career low. Despite this, during the 1942 World Series, he led all Cardinals' hitters in batting average with .300 en route to their World Series victory.

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Wikipedia