- Kennedy, W. T1
- Kimball, Ingalls, 1874-19331
- Kirchmayer, Johannes, 1860-19301
- L & M Co. [Designer]1
- L.A. Thompson Scenic Railway Company1
- Lambert, Samuel W. (Samuel Waldron), 1859-19421
- Largajolly, H.G. [Photographer]1
- Leete, Louise Grosvenor1
- Lethaby, W. R. (William Richard), 1857-19311
- Léon, Maurice, 1880-1
- Lloyd (Troy, N.Y.) [Photographer].1
- Ludlow, William S1
- Macy, Valentine Everit, 1871-19301
- Maginnis, Charles Donagh, 1867-19551
- Mangels, William F., 1867-19581
- Manning, Warren H. (Warren Henry), 1860-19381
- Mathews, Charles Thompson, 1863-19341
- Maxim, Hiram S. (Hiram Stevens), 1840-19161
- Mayers, Murray & Phillip1
- McBee, Silas, 1853-19241