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 the spatial patterning of religious denominations. One of his most ambitious and imaginative projects was a provocative assessment of the impact of increasingly powerful personal preference on the spatial character of American society.
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. During 1972–1973 he served as the first Director of the Population Issues Research Center (what would become the Population Research Institute at Penn State).[6]
In 1973, Zelinsky published The Cultural Geography of the United States. In addition to his research in popular culture, he made substantial contributions in the fields of "population" and "folk geography".
Zelinsky's Theory of First Effective Settlement was that the dominant culture of a nation is defined by the first settlers who came to an area who are able to effect a self-perpetuating society. The theory states that these first settlers have significant impact on the social and cultural geography of the area, however few these first settlers may have been. They lay the groundwork for the following generations and are perhaps more important than the contributions of thousands of new immigrants generations later.[7]Colin Woodard further expands upon this theory in his book, American Nations.[8]
