"Building the Union Pacific, Nebraska." Woodcut from sketch by Alfred R. Waud, 1867

During this time illustrations for magazines and newspapers were done by illustrators. There was no way to transfer a photograph to a printing plate at this time. The halftone process had not yet been invented. An artist such as Waud would do detailed sketches in the field, which were then sent by courier back to the main office of the newspaper or magazine they were working for. A staff of  engravers would use the sketches to create engravings on blocks of boxwood.  The wood engravings were then copied via the electrotype process which produced a metal printing plate for publication.