The Soundex Indexing System - To use the census soundex to locate information about a person, you must know his or her full name and the state or territory in which he or she lived at the time of the census. It is also helpful to know the full name of the head of the household in which the person lived because census takers recorded information under that name. The soundex is a coded surname (last name) index based on the way a surname sounds rather than the way it is spelled. Surnames that sound the same, but are spelled differently, like SMITH and SMYTH, have the same code and are filed together. The soundex coding system was developed so that you can find a surname even though it may have been recorded under various spellings. This has been added to Finding People Subject Tracer™ and Genealogy Resources Subject Tracer™ Information Blogs.