Having trouble finding your family surname in the Ancestry or HeritageQuest online indexes to the federal censuses? The Soundex indexing system helps you find an individual name among the millions listed on the microfilm of the 1880, 1900, and 1920 censuses. The advantage of the Soundex code is that variations and inaccuracies in spelling do not affect the coding of the names. The code uses the first letter of the surname, combined with a 3-digit code for the rest of the name.