its peak in the 60s and 70s. Golf was always on TV and majors were must see and invariably were on the cover of Sports Illustrated, "the" indicator of sports popularity before cable and internet. Arnold Palmer was insanely famous and popular--every bit the phenom Tiger was but with a less prickly personality. True golfing greats like Gary Player, Lee Trevino and Tom Watson were competing head to head with Jack while really good players like Johnny Miller, Tom Weiskopf, Tony Jacklin, Billy Casper and flamboyant Chi Chi Rodriguez were capable of winning any tournament.
Golf's popularity took a huge plunge for me after Palmer, Nicklaus and Trevino aged out in the 90s and the talent and star power of the 90s players took a dive. Tiger revived interest in the 2000s for sure.
Adjusting for 120 million more people in the US today than then, I would bet golf then was more popular then than during Tiger's heyday.