Refer to the "Historical Context: Selected Books" page for campus building information and photos on campus (especially Parson's 1968 The Cornell Campus and Altschuler and Kramnick's Cornell: A History, 1940-2015 For a concise history of a particular building, try searching Cornell Fact Search.
Building plans are available to students working on projects from Facilities and Campus Services. To obtain building plans, follow the Student Project Procedures on the Facilities and Campus Services--Building Information and Documents webpage. Note: "Plan adequate time, material may not be available on a short turn around, or not available due to security issues." [--Archiving Services]
The University Archives in the Rare and Manuscript Collections has a clippings file on a large number of specific Cornell buildings; ask at the RMC reference desk, 2B Kroch Library. Also in RMC, the Cornell Clippings File and the ClipFile Index has information from local newspaper clippings about some Cornell buildings (dedications, fires, demonstrations, etc.).
For exhibits and tours of library buildings, refer to the "Digital Collections" page.