Percent Prime-Age High School or Less Working Part Time Source: Authors’ compilation based on 1950–2000 census and 2005–2015 American Community Survey data (Ruggles et al. 2019). Percent Prime-Age High School or Less Working Part Time Source: Authors’ compilation based on 1950–2000 census and 2005–2015 American Community Survey data (Ruggles et al. 2019). Note: Lines computed from locally weighted regressions of the percent of prime-aged part-time workers in a commuting zone against variables indicated along the x-axis, separately by year. Bandwidth = 0.6. Tom VanHeuvelen, and Katherine Copas rsf 2019;5:77-103 © 2019 Russell Sage Foundation. VanHeuvelen, Tom, and Katherine Copas. 2019. “The Geography of Polarization, 1950 to 2015.” RSF: The Russell Sage Foundation Journal of the Social Sciences 5(4): 77–103. DOI: 10.7758/RSF.2019.5.4.03. Direct correspondence to: Tom VanHeuvelen at tvanheuvelen@gmail.com, Department of Sociology, 909 Social Sciences Building, 267 19th Ave. S, Minneapolis, MN 55455; and Katherine Copas at kcopas2@illinois.edu, 3059 Lincoln Hall, 702 S. Wright St., Urbana, IL 61801.