Data from the 1990 census at the block level are available from 1990 Summary Tape File 1B (Tape or CD-ROM). You can contact your local State Data Center (http://www.census.gov/sdc/www/) for assistance or purchase the tape or CD-ROM from our Customer Services Center. Their telephone number is 301-763-4636.
We are in the process of decommissioning the e-mail address
Again, we appreciate your interest in our data.
So, no, 1990 block data is NOT available from American Factfinder. 1990 block group data, yes; 2000 block data, yes.