Creating a comic like Steve Canyon or Terry and the Pirates involves a lot of tasks besides drawing. Milton Caniff laid out his studio to have separate workspaces for different parts of his job. Click to enlarge the picture.
Under the large north window are two drawing tables (penciling and inking?), but also bookshelves, a model of an airplane and a jeep, filing cabinets, a typewriter, a globe, a writing desk, a barometer, a radio, four fluorescent task lights and a wood floor.
The Norman Rockwell Museum currently has an exhibition through May 25 featuring artists in their studios. The Rockwell exhibit includes photos of the ateliers of John S. Sargent, N.C. Wyeth, and William Merritt Chase (though I don't think they include Milton Caniff). For more info, link.
The photo of Caniff's studio courtesy of ASIFA, Hollywood Animation Archive, link.