Is there a way to get township level data, specifically for ethnicity/nativity/citizenship status in 1900 & 1920?
In pre-1950 samples, low levels of geography are identifiable in public use data. Specifically, INCORP and MCD are available in 1900 and 1920. While these are close to “township” they are not quite exact. So, the IPUMS USA project may not be able to provide quite the information you are looking for. If you are looking for aggregated data at the township level, you may want to look into the tables available via the IPUMS NHGIS project. Due to data aggregation, NHGIS data is often identifiable at much lower levels.