This project complicates and expands upon the Genettian concept of paratext, focusing on paratextual functionality and meaning-making practices related to the development of American mass media during the 19^th, 20^th, and 21st centuries. Utilizing Ellen McCracken’s “interior” and “exterior” pathways as a basis for paratextual vector analysis, this dissertation examines paratextual functionality in four case studies focusing on the late 19th-century newspaper advertising of John Wanamaker, the WWII-era radio serial Captain Midnight, the 1950s television program The Disneyland Story, and the comment section of Breitbart News during the second decade of the 21^st century.