| L'histoire universelle de tous les oyseaux de l'univers |
| LVNG. Records |
| Lach, Donald F. Papers |
| Ladurelle. Maimoire pour servir […] la cuisine |
| Lafayette Manuscripts |
| Lafayette-Bonaventure. Collection |
| Laing, Gordon Jenning. Papers |
| Lamson, Charles Henry. C. H. Lamson's Experiments on Kite Flying |
| Lan, Ching Huong . Watercolor Sketches Showing Details of Buying, Curing, Packing, and Shipping Tea |
| Land Grants. Collection |
| Land Indenture Document |
| Landahl, Karen. Papers |
| Landesco, John. Papers |
| Lane, Ebenezer, Family. Papers |
| Lang, Harvey. Collection |
| Lange, Oskar. Papers |
| Langenbeck, Conrad Johann Martin. Chirurgie |
| Langley, S. P., The Internal Work of the Wind |
| Langley, S.P. The Langley Aerodrome |
| Lanza, Gaetano, Train Resistance |
| Lanzl, Lawrence H. Papers |
| Larkin, Emmet. Papers |
| Latham, Vida Annette. Papers |
| Latimer, Ronald Lane. Papers |
| Latin Bible, scattered leaves. Manuscript (Ms 122) |
| Laughlin, James Laurence. Papers |
| Laves, Gerhardt. Papers |
| Le Baron, William. Papers |
| Le Count, Edwin Raymond. Papers |
| Leacock, Stephan Butler. Papers |
| League of Nations Association, Midwest Branch. Records |
| Lecture Notes. Physiologie von A.F. Hempel |
| Lee, Elon N. and Edson S. Bastin. Papers |
| Leites, Nathan. Papers |
| Leland, Simeon E. Papers |
| Leo I, Pope, Sermones. Manuscript (Ms 30) |
| Leopold, Nathan F. Collection |
| Les Narbonnais : chanson de geste. Manuscript (Ms 708) |
| Leslie, Leonie. Correspondence |
| Letters to Robert Browning and Elizabeth Barrett-Browning |
| Levi, Edward H. Inauguration. Records |
| Levi, Edward H., Papers |
| Levine, Donald. Papers and Addenda. |
| Levinson, Salmon. Papers |
| Levy, Ernst. Papers |
| Lewis, Edwin Herbert. Papers |
| Lewis, Eva Overton and Julian Herman Lewis, MD, PhD Collection |
| Lewis, Fielding. Papers |
| Lewis, Leon. Papers |
| Lewis, Ralph. Papers |
| Lewis, Sinclair, and Josephine Weil Meyer. Correspondence |
| Library Quarterly. Records |
| Lilienthal, Otto. Clippings and Photographs on the Lilienthal Flyer |
| Lilienthal, Otto. Papers on Aeronautics |
| Lillie, Frank R. Papers |
| Lillie, Ralph S. Papers |
| Limited Editions Club. Collection |
| Lincoln Collection. American Historical Portraits |
| Lincoln Collection. American Political Cartoons |
| Lincoln Collection. Art, Artifacts, and Ephemera |
| Lincoln Collection. Barton Codex Manuscripts |
| Lincoln Collection. Broadsides |
| Lincoln Collection. Cartoons, Drawings and Photographs |
| Lincoln Collection. Charles Edwards Wilcox. Civil War Diary |
| Lincoln Collection. Currier & Ives Lithographs |
| Lincoln Collection. Lincoln Law Cases |
| Lincoln Collection. Lincoln Miscellaneous Manuscripts |
| Lincoln Collection. Lincoln Portraits |
| Lincoln Collection. Monuments and Memorials |
| Lincoln Collection. Osborn H. Oldroyd. Collection |
| Lincoln Collection. Publications and Newspapers |
| Lincoln Collection. Robert S. Todd. Papers |
| Lincoln Collection. Sheet Music |
| Lincoln Collection. William E. Barton Collection of Books from the Lincoln and Herndon Law Library |
| Lincoln Collection. William E. Barton Collection of Lincolniana. The John Hay Library |
| Lincoln Collection. William E. Barton. Papers |
| Lincoln, Adaline. Papers |
| Lincoln, Edwin Hale. Sailing Vessels. Photographs |
| Lincoln, Robert Todd. Collection |
| Lindblad, Andrew. Collection |
| Linford, Alton, Papers. |
| Link, Adeline De Sale. Papers |
| Linné, Carl von. Species plantarum exhibentes plantas rite cognitas, ad genera relatas, cum differentiis specifis, nominibus synonymis selectis, locis natalibus, secundum systema sexuale digestas |
| Lipson, Lillian Rose Witz, Alumni Collection |
| Llewellyn, Karl N. Papers |
| Lloyd, Alice. Papers |
| Llull, Ramon, Ars Brevis |
| Loeb, Hedwig L. Papers |
| Longstreet, Stephen. Collection |
| Lorie, James. Papers |
| Lous, Christian Carl. Arithmetica, Geometrien, Trigonometrien, Longimetrien, Transformationen |
| Lovett, Robert Morss. Papers |
| Lowden, Frank O. Papers |
| Lowinsky, Edward E. Papers |
| Lowitz, Leza. Papers |
| Lucan, Pharsalia. Manuscript (Ms 33) |
| Luckhardt, Arno B. Papers |
| Lunde Family. Papers |
| Léveillé, Hector. Catalogue illustré et alphabétique des plantes du Seu Tchouen |