I am looking to download median household income from 1900 to date but I can find the code associated it IPUMS.
Similarly, how do I obtain data for different occupational sectors from 1900.
Most of the IPUMS products provide microdata (individual records containing information collected on persons and households), which means you would need to use a statistical tool (Stata, SAS, SPSS, etc.) to calculate median income from an income related variable (either at the household or person level).
IPUMS NHGIS provides spatially aggregated summary data and it looks like there are several time series tables available for median income. Unfortunately, it does not look like this information is available back until 1900.
If you are interested in data back until 1900, it looks like your best option will be to look into using IPUMS USA. We have some video tutorials available here to help get you started.