Carl Leavitt Hubbs (1894–1979) was a prominent and internationally renowned American ichthyologist whose publications include taxonomic descriptions of several North American blindfishes including the Mexican Cave Characin. His archived personal papers reveal a wide-ranging interest in the biology and evolutionary origins of cave and blindfishes, and his discussions and disputes with colleagues about their taxonomy. He also took opportunities to collect other fauna from American caves during the inter-war decades. Drawing upon his unpublished archive and other relevant sources his biospeleological work is chronicled in detail and discussed in the context of his other work.