I’ve heard that in the past most people simply went to their regional university, so it was not particularly difficult to get into a school like Harvard or Yale. When did these elite colleges raise academic standards to such a high level that they are now extremely difficult to get into?
You may be interested in this previous answer of mine, as well as /u/UrAccountabilibuddy's answer in the same thread.
The TL;DR version is: it was always difficult to get into Harvard and Yale. The entrance "exams" were more like interviews and required the applicant to be able to translate Greek and Latin texts into English, and even converse in Greek and Latin with the admissions officer. The only type of student who was likely to have that ability was someone from an elite, upper-class family who could afford to have hired a private tutor growing up, before applying for admission to the college.