This piece of All-Time American Rugby Players recognition comes in large part thanks to ivyrugby.com.

In the late 1800s colleges played a form of football that was essentially rugby. Over time they adopted rules variations (much as Aussie Rules, Gaelic Football, and Association Football did) and turned it into American Football.

But teams from the Ivy League played what was much closer to rugby than it was to football in the 1870s, and those players are recognized, at least by historians, as pioneers for both games. These players were led by Walter Camp of Yale and Eugene V. Baker of Princeton. Camp especially pushed for some rules changes, the most important one being that a try should count for some points. At the time, crossing the goal line and touching the ball down only allowed you an unimpeded attempt to kick at goal (to "try" to kick at goal). This was true in the early days of all rugby. Camp, who was pretty good at making it across the goal line, wanted tries to count for something on their own.

He wasn't alone, and eventually Rugby adopted such a notion. But before it did, Camp had pushed for a few more rules changes that led to the development of American Football. 

There is a longer and much more fascinating article on this at IvyRugby.com here>>.

But while they were playing rugby, the Ivy Leaguers were pretty good at it. Here is our recognition of the best, as stated by Camp in 1904 (with the addition of Camp himself, as Walter Camp declined to list himself as one of the top players of the time):

J.S. Harding, Yale, Forward
John Moorehead, Yale, Forward
Bland Ballard, Princeton, Forward
J.E. Cowdin, Harvard, Forward
Walter Camp, Yale, Halfback
W.D. Hatch, Yale, Halfback
Oliver D. Thompson, Yale, Halfback
W. Earle Dodge, Princeton, Halfback
Theodore M. McNair, Princeton, Halfback
R. Winsor, Harvard, Halfback
Eugene V. Baker, Yale, Back Threequarter
Robert Bacon, Harvard, Back Threequarter

(Halfback probably means scrumhalf or flyhalf)