Years with Boston: 1936-1942 (.320/.429/.605, 222 home runs, 788 RBIs, 1,051 hits)
Best Year in Boston: 1938 (.349/.462/.704, 50 home runs, 175 RBIs, MVP)
Foxx immediately stepped into the core of Boston's lineup and set the team record for home runs, breaking Babe Ruth's 1919 mark of 29. In 1938, he broke his own team record by hitting 50 home runs, and that record would stand until 2005 when David Ortiz hit 54 home runs. Foxx led the league in batting average and RBIs in 1938 and missed the triple crown because Hank Greenberg hit 58 home runs. He also led the league in on base percentage and slugging percentage.
Foxx's numbers dipped a little bit in 1939, but by that season he was no longer the only slugger on the team. Foxx helped Ted Williams along in his early years in the Major Leagues and protected the young slugger in the lineup. Foxx's numbers again dropped in 1941, hitting just 19 home runs, but he still lead the league in walks and hit .300.
Unfortunately Foxx's numbers would continue to decline after that. He played in just 30 games with Boston in 1942 and was placed on waivers, being selected by the Cubs. He played just two more seasons after that and retired.
Foxx was elected to the Hall of Fame in 1951, his sixth year on the ballot, though that is largely because the rules were not well-formulated at that time and he was nominated immediately after he retired. Most voters thought he should wait a few years. Foxx wears a Red Sox cap on his Hall of Fame plaque. Though he had some terrific years in Boston, his time with the A's is what most people associate with Jimmie Foxx. His time in Boston was important to his election to the Hall of Fame, but not the most important.