How would i go about finding neighborhood demographics data for the neighborhoods I lived in during 1990 and 2000? I would prefer something more detailed than city data. I want to split the data down to the level of the few surrounding neighborhoods.
The closest to a "neighborhood" might be an area known as a census tract. You can look up the census tract IDs for the neighborhood you're interested in using the Reference maps found here: https://www.census.gov/geographies/reference-maps/2000/geo/2000-census-tract-maps.html for 2000 and here https://www.census.gov/geographies/reference-maps/1990/geo/1990-census-tract-maps.html for 1990.
Then look for historical data for those tracts from the 1990 Census and 2000 Census. https://www.census.gov/main/www/cen2000.html
Another option might be to contact your local State Census Data Center for help finding the correct data: https://www.census.gov/about/partners/sdc/member-network.html
In my experience, tracts are a very poor substitute for neighborhoods. I was recently tasked with comparing both tracts and ZCTAs to designated neighborhoods in St. Louis. The takeaway: Tracts are better than ZCTAs, but neither one is a good or even "close-enough" fit. Your mileage may vary of course.
(tracts green, neighborhoods red)