The ethnic segregation of immigrants in the US from 1850 to 1940

Interesting piece by Katherine Eriksson and Zach Ward:

Those opposed to immigration often contend that immigrants are slow to assimilate. This column takes a longer-term view of assimilation by looking at the degree of ethnic spatial segregation in the US during and after the Age of Mass Migration. New methods and newly digitised data suggest that segregation in the US between 1850 and 1940 was both higher and more widespread than previously thought. However, despite slow rates of spatial assimilation, immigrants tend to assimilate culturally at a fast rate. 

How researchers are using really old historical records which are now being increasingly available thanks to digitization.