Ken Boyer was born in Liberty, MO, he went to high school in Alba, MO (just outside of Joplin), and he died in St. Louis, MO in 1982. While Boyer isn't directly from St. Louis, he spent his final years there, he played for the Cardinals, and he spent his formative years in a city that has plenty of Cardinal baseball fans.
Boyer spent 11 seasons in St. Louis as a player. In those 11 seasons, he went to 7 All-Star Games, won an MVP award, and won a World Series in 1964. Boyer garnered 62.8 bWAR in his 15-year career, and he surprisingly is not in the Baseball Hall of Fame. The third baseman has the accolades and statistics to make the Hall of Fame, but he is no longer eligible.
One of the best catchers ever, Yogi Berra was born in The Hill in St. Louis. Berra is so famous to that area of the city that his family's old house on The Hill has a placard out front that reads "Hall of Fame Place". The first-generation Italian-American played 19 years in MLB, all of which were with the New York Yankees. Yogi made his debut on September 22nd, 1946, and his final game was on May 9th, 1965. He died on September 22nd, 2015, 69 years after his inaugural MLB game.
Berra played in 2,120 games in his career, and he was an All-Star in 18 of his 19 seasons (missed only in his Rookie year, where he was still MVP-15). He won the MVP award three times, and Berra helped the Yankees win 10 World Series titles during his tenure. Yogi racked up 59.5 bWAR in his entire career. He was, and still is, one of the best catchers to have ever played the sport.