I can't speak to anything too far in the 19th century or for the UK antiquity, but for American golf:
1894 - all of the scattered pre-history comes together in the germination of a national body and a sanctioned national tournament.
1916 - Jones debuts at Merion, PGA is formed- 1st PGA is played; First Era in GCA about to yield to Golden Age.
1931 - Jones first year in retirement, making films, purchases Fruitlands, steel shafts win the US Open, Golden Age course building ends markedly in the throes of the Depression.
1951 - RTJ first year as "Monster" Open Doctor at Oakland Hills, framing Hogan's amazing return and consecutive victories. Oilman R.J. Jackson receives patent and starts manufacture of first dedicated electric golf cart - "The Arthritis Special."
1962 - IMG's Big Three win all 4 pro majors, Palmer on consecutive Opens, completing the re-elevation of the tournament; Nicklaus 1st and Player's 2nd. Golf is led by TV and player image forever since; following on, a new era of course building roars.
I've got to think about the the last 60 years before continuing...