The "Institute History" tab has some great primers. The blog posts are good too.
Digital Collections includes scanned resources. Most notably, all Polytechnic articles are scanned here. I recommend searching by year to get some structure to the system. It's difficult to use at first but you get used to it. Do not try to use on mobile.
The Guide to the Archives has all of the titles of the in-person archival resources.
My biggest piece of advice: learn how to use the Guide before you try to go to the archives. You can and should request a particular resource. Obviously the archivists are super knowledgeable about most topics, and if you can't find something, you can ask for help. But ideally, you submit a request for "AC 13 Grosh Presidential Files Boxes 24, 26, 32" and then go in and look at them. It makes everything so much faster if you know what you're looking for first. Going in and saying "can you find me the history of chemistry at RPI?" is like walking up to an engineer and saying "can you build me a rocket engine real quick?"
Also I cannot express my undying love for Jenifer, Tammy, and Kelsey enough. A crack team. If I had a million dollars I would give it to them.
I'm including ones I consider to be proper "histories" of RPI. All published histories can be found at the archives website, and include special topics like alumni history, chemistry, architecture, and more.
Phelan's "Rensselaer, where imagination achieves the impossible : an illustrated history of Rensselaer Polytechnic Institute", 1995 is a beautiful piece of art. Phelan worked as a chaplin, professor, dean and historian for years. His perspectives show a true pure love for RPI. It is a little light on covering political controversy, but its more than made up for by the way he integrates photos. A great "coffee table" read, when you just want a little taste of history for your evening. Goes to the 1990s.
Rezneck's "Education for a technological society : a sesquicentennial history of Rensselaer Polytechnic Institute", 1968 is a proper history written by a proper professor of history. You cannot cherrypick this one the way you can Phelan. It's dense, and it's not an easy read, and everything is self-referential, but it also doesn't pull punches. Rezneck provides a ton of really thoughtful insights into RPI's history. If you're a history buff or are super into politics, read this. Goes to the 1960s.
Ricketts' "History of Rensselaer Polytechnic Institute, 1824-1934" 1934 is the original history of RPI. Ricketts served as president form 1901 until his death in 1934, and during that time he completely transformed RPI for the new century. Remember, enrollment went from about 200 to 1500 in this time, and he saw it all. He was an engineer, so his history is not as technically well-written as Rezneck's or Phelan's. However, he was clearly a systems thinker, and Ricketts' defined RPI in a way that few others ever did and ever will. His insights are particularly unique because of these experiences. He rarely cites anything, because he lived through most of it. Goes through 1930s.
Honorable mention: Ricketts' History of Rensselaer Polytechnic Institute, 1824-1924
"In the beginning I planned this sketch---for it is little more---as a slight memorial of the hundredth anniversary of the foundation of Rensselaer Polytechnic Institute. Before I had delved far in its history, however, I realized that I was dealing with a subject of no parochial concern; that, for half a century, the institute was one of the intellectual centres of America... I have tried, therefore, to marshal the achievements of Amos Eaton and Steven van Rensselaer in proper perspective and to indicate the national significance of much that has seemed of mere local interest."