Brown University, Columbia University, Cornell University, Dartmouth College, Harvard University, Princeton University, the University of Pennsylvania, and Yale University make up the Ivy League. Obviously these schools are all top notch, and the term has come to be a synonym for American's most elite universities. But while it seems "Ivy" has a history of use predating 1954, the Ivy League is properly an athletic conference these schools make up. So:
Prior to the establishment of the Ivy League proper, were these schools a special group in the public mind?
If not, was there something similar to our current perception of the "Ivy League"?
If so, was it only those eight, or might other schools also have fallen into that group, but ended up excluded from the Athletic Conference for whatever reason?
This isn't exactly an answer, but it gets at some of what you ask. The current Ivy League is related to the older concept of the Colonial Colleges. There were 9, all founded before the American Revolution. These include every current Ivy except Cornell (founded in the 19th century) as well as two non-Ivies (William & Mary and Rutgers). In terms of age, prestige, and famous alumni, this was a fairly similar group.
*Source: Creating the American Mind: Intellect and Politics in the Colonial Colleges; J. David Hoeveler