TITLE: Why Cohen-Macaulay rings have become important in commutative algebra?
QUESTION [35 upvotes]: I want to know the historic reasons behind singling out Cohen-Macaulay rings as interesting algebraic objects. 

I'm reviewing my previous lecture notes about Cohen-Macaulay rings because now I'm studying about Stanley-Reisner rings and I think I need to have a better general understanding about why I need to study CM rings.

REPLY [5 votes]: Richard Stanley's description on How the Upper Bound Conjecture was Proved tells much about the history of how Cohen-Macaulay rings became important in combinatorics. Additional links can be found here.