Special collections with rare or historical documents, sheet music, recordings, and ephemera can be excellent sources for your research. We are highlighting several collections on this page that you can browse here in person (in the case of the UIUC special collections materials) or online (in the case of collections beyond UIUC).
Keep in mind that archives work a little differently from libraries - you usually can't just show up without planning ahead. You may need to coordinate your visit in advance to give the archivists time to pull and prepare materials for you to look at. It's also important to note that archival materials cannot be checked out, you'll have to look at them during your visit, so plan to visit when you have some time to spend with the materials!