Billy Williams played the first 14 of his 16 seasons with the Chicago Cubs, where he quickly established himself as one of the best hitting Leftfielders in the game.  Williams would win the Rookie of the Year Award in 1961 with a 25 Home Run season.  Power would be a big part of his game, as he blasted 20 or more taters the next 12 seasons and a career-high of 42 in 1970.  That year, the six-time All-Star would lead the NL with 205 Hits, and 137 Runs Scored, and Willians would have a .322 Batting Average, and he was second in MVP voting.  Williams would again be the runner-up for the MVP when he won the Batting and Slugging Title and went deep 37 times.  

Ron Santo would crack the Majors with the Cubs in 1960, and the Third Baseman would quickly establish himself as one of the premier men at the hot corner, both with his bat and glove over the next decade-plus.  Santo would tabulate an impressive 2,171 Hits as a Cub and even more impressively knew the art of getting on base.  Santo led the NL in Walks four times and was a two-time leader in On Base Percentage.

Ryne Sandberg arrived in Chicago via one of the most lopsided trades in baseball history as the future Hall of Fame arrived with Larry Bowa for Ivan DeJesus.  Sandberg was converted to an infielder, and after playing only six games in the Majors with Philadelphia, he would be converted from Outfield to Third Base (he would then move to Second a year after)

In terms of overall iconic status at Wrigley Field, Ernie Banks would be number 1. 

Of course, he would!  He is "Mister Cub" after all!