Zelinsky made numerous geographical studies of American popular culture, ranging from the diffusion of classical place-names to spatial patterns of personal given names and to the spatial patterning of religious denominations.
During the 1960s, along with Gordon DeJong, Warren Robinson, and Paul Baker, Zelinsky helped launch a population research center and coordinate an interdisciplinary graduate instructional program in population studies at Penn State and thus helped lay the foundation for what would become the dual-title Graduate Program in Demography.