Looking at my copy of the 1970 Transit, I see a number of references to a rally that was held in March of that year. On page 50, there is a photo of the front page of the March 11, 1970 edition of The Polytechnic, with an article headlined "Library tour ends successful rally," accompanied by a photo of a long line of students captioned "Students closed the rally with peaceful march to library." At my age, it's a little difficult to read the body of the article without a magnifying glass, but there appears to be a reference to as many as 2,000 students participating in the rally.
Might this be the protest you remember, Ralph, or was there another protest the next year, as well?
Other articles on the front page of that March 11 Poly were headlined "Teach-ins to emphasize discussion of Requisites" and ""Meaning of 'University' probed." Elsewhere in the same Transit there are interviews with members of the student body at the time, expressing their frustration over what they perceived as Dr. Richard Folsom's unwillingness to respond to their opinions about things that needed to change at RPI - one of which was the library.
For those who feel that Dr. Jackson's administration marks the beginning of the end for RPI, be assured that 46 years ago there were those who felt that Dr. Folsom's administration would mark the beginning of the end - and RPI is still there.