This is a subject I'm very interested in myself, and one that seems not particularly well covered in the various books I've read on cinematography or film style history. 24mm was indeed very wide when Toland shot Citizen Kane, the widest professional cine lens available at the time, as far as I'm aware. Despite there having been very wide angle lenses since the beginning of the 20th century, including over 90 degree fields of view from lenses designed for large plate architectural photography