Population data per county were acquired in plain-text, tab-delimited format. To make these data geospatial in nature and prepare them for analysis, a Python script was written to parse the text file and output a suitably-formatted result to a comma-separated values (CSV) file. The utilized Python source code is available at this project's GitHub repository.
In ArcGIS Pro, said CSV file was joined to TIGER/Line county features. The resulting features, with populations from 1790 to 1990 now present, were spatially joined to core-based statistical area (CBSA) features. The layout of the 2000/2010 CBSA population spreadsheet was configured to allow for import into ArcGIS Pro, then these figures were joined to the CBSA features.
The CBSA polygon features, with all years of population now joined, were converted to points to eliminate unneeded data for proportional symbol symbolization. The result was exported to a GeoJSON file.
This web application reads said GeoJSON file via AJAX and stores the received data in an object, waiting to add it to the map when requested. After a request for display is made, the vintages of data in question are read from the object and a sort of histogram is built to determine what size the point symbol for each CBSA should be. The minimum and maximum sizes allowed vary based on the map's zoom level, and only those population figures in the first to 99th percentiles are used to create the histogram to prevent outliers from adversely affecting the symbolization.
The most-populated parts of Alaska are administratively organized into county-like divisions termed "boroughs". The majority of the state, however, remains unorganized. To facilitate a census throughout the state, even in unorganized territory, the US Census Bureau has created divisions named "census areas". These census areas form the basis of the core-based statistical areas (CBSAs) that are symbolized in this map. These census areas have only been in use since the 1960 Census, however, meaning that data from before this time are not readily relatable to modern-day CBSAs. As a result, pre-1960 population data for Alaskan locales are not provided in this map.