Joe,
In 1900 there 982 golf courses (C&W)- pop. 76,094,000(U.S.Census)
In 1915 there were 3,000 golf courses (Am. Golfer). (pop. 100,546,000)
In 1915 there were estimates of between 2 and 3.5 mil players and it was conjectured that there were only 5,000 players in 1905
There were 5, 856 golf courses in the US in 1930, and 5,745 in 1958(USGA)
In 1958 (pop-174,881,904) there was 1 golf course for every 30,461 people.
In 1930 (pop- 123,076,741) there was 1 golf course for every 20, 833 people.
In 2008 (pop- 308,000,000) there was 1 golf course for every 19,250 people.
An estimated 3,970,000 men, women and juniors played at least ten rounds of golf during 1958, an increase of 290,000 regular golfers over 1957.(USGA)
25mil golfers played 500mil rounds in 1997,( pop 267,743,595) same as in 1990 (NGF)
(pop 249,438,712), but there were 23% more courses in 1997 than in 1990
High water mark for number of golfers was 30 mil.in 2005, roughly 10% of the population.(NGF)