I downloaded some GIS boundary files, but where is the census data?

I downloaded some GIS boundary files, but where is the census data?

GIS boundary files, on their own, do not contain any census data, even if you downloaded the data tables at the same time. To attach tabular NHGIS data files to the GIS boundary files requires a join operation in your GIS software. Additional information on using a GIS with NHGIS data can be found on the User?s Guide page.