The modern way to identify birds in the field may be to run an app on a smart phone. But in earlier times (and for some of us even now) bird identification involved consulting books that were made of paper.
Here I describe some field guides from the 1st half of the 20th century that include the California condor. These are books that were (and still are!) useful for identifying bird species. These are also books small enough to be readily carried. My maximum size limit is Alvaro Jaramillo’s beautiful new Field Guide to Birds of California: