(Contributors: Thomas Peer and Conner Burtner)
The maps below are based on data from the 1920 census for Colorado. The 1920 census asked not only where people were born, but also where their mothers and fathers were born. Thus we can visualize an approximation of change over time in migration patterns.
Figures 1 and 3 show the birthplaces of Colorado residents in the United States and Europe, respectively, and figures 2 and 4 show the birthplaces of the mothers of those residents. So, what you can see in these maps is where those who lived in Colorado were born, as well as where their families originated from (note: we are using only mothers’ birthplaces here, but we did some tests with fathers’ birthplaces, and the results are very similar.) If you hover over the maps, you can see how many people there were from each of those countries/states.
We separated the United States and Europe so that it would be easier to visualize; as you see if you look at the figures closely, the vast majority of Coloradans – about 34 percent of the total – were born in Colorado, so the choropleth (shaded region) maps work better (have a clearer color range) if we keep the smaller European-born population on a separate map.
Overall, in 1920 about 13 percent of U.S. population was foreign-born; this was also the percentage in Colorado. About 20 percent were second-generation immigrants (that is, their parents had immigrated but they themselves were born in the United States.)
These maps don’t, of course, show Asia, Africa, or the Americas beyond the United States. About 80 percent of immigrants in Colorado in 1920 were from Europe; of the remainder (about 22,000 individuals), about half were from Canada.
Figure 1: Birthplaces of people who lived in Colorado in 1920, United States
Figure 2: Birthplaces of the mothers of people who lived in Colorado in 1920, United States
As you can see in the maps above, the main feeder states for Colorado were the midwest corridor stretching through Kansas and Nebraska to Illinois, Ohio, and all the way to New York state.
Figure 3: Birthplaces of residents of Colorado in 1920, Europe
Figure 4: Birthplaces of mothers of residents of Colorado in 1920, Europe
The similarity of the maps of foreign birthplaces of residents and of residents’ mothers seem to imply that as far as the residents of Colorado were concerned, immigration patterns had apparently not changed dramatically in the decades preceding 1920 (though it should be noted that this takes ALL mothers and ALL residents who are born in Europe –that is, it is not limited to e.g. only the mothers of native-born residents, and thus any potential change over time would not be displayed here as starkly as it might be.)
If one looks at the numbers or percentages, though, one can see that the national trend of immigration shifting from Northern and Western Europe toward Eastern and Southern Europe and toward countries beyond Europe is visible in Colorado as well. The graph below shows foreign countries ordered by whether more individuals were born in that country than had both parents born in that country or vice versa.
Figure 5: Individuals with foreign-born mothers vs. foreign-born individuals, by country. The basic calculation is percentage of the Colorado 1920 population consisting of native-born individuals with mothers born in that country minus the percentage of foreign-born individuals with mothers born in that country. Negative numbers (representing more recent immigration) are in red, positive in blue. Only populations of >1,000 are included.
(These maps are made with Google Sheets; for instructions how to make maps like these, you can check out this post at the Geoawesomeness site.)