New Area- and Population-based Geographic Crosswalks for U.S. Counties and Congressional Districts, 1790–2020

In applied historical research, geographic units often differ in level of aggregation across datasets. One solution is to use crosswalks that associate factors located within one geographic unit to another, based on their relative areas. We develop an alternative approach based on relative populations, which accounts for heterogeneities in urbanization within counties. We construct population-based crosswalks for 1790 through 2020, which map county-level data across U.S. censuses, as well as from counties to congressional districts. Using official census data for congressional districts, we show that population-based weights outperform area-based ones in terms of similarity to official data.