Why can’t I download data at the census tract level from before 1910?
Census tracts did not exist before 1910. NHGIS only has data tables and GIS shapefiles for areas defined by the US Census Bureau. In addition, it is important to remember that not all levels of census enumeration have shapefiles associated with them.
For example, while data tables can be downloaded at the American Indian Reservation [excluding trust land] level, NHGIS does not have a corresponding GIS shapefile.