The library has microfilm versions of the original manuscript returns for the Federal Population Censuses for Pennsylvania, 1800-1930.
Much of the 1890 Census was destroyed by fire. A partial substitute for Centre County is:
The 1880-1920 Censuses on microfilm are indexed using the Soundex system. Soundex arranges last names based on how a name sounds rather than how it is spelled. Surnames that sound the same, but are spelled differently, like SMITH and SMYTH, have the same Soundex code and are filed together. The Soundex coding system was developed so that you can find a surname that may have been recorded under various spellings.