What is Soundex?
The Soundex indexing system codes surnames based on their sound rather than their spelling. "The Soundex coding system was developed so that you can find a surname even though it may have been recorded under various spellings," writes the National Archives and Records Administration (NARA) on their website, giving "Smith," "Smyth," and "Smythe" as examples.
Created in the early 20th century, Soundex was used by the Census Bureau during the Depression to both act as a public works project and to provide information to the government as it implemented Social Security. The 1900 and 1920 censuses, as well as parts of the 1880 and 1930 censuses, were Soundexed. NARA also has several INS passenger lists, ranging from the early 20th to mid-20th century, which are Soundexed. State and local archives may also have some of their records indexed with this method.
What do the Soundex codes mean?
Each code starts with the first letter of the surname followed by three numbers. Soundex numbers range from 1 to 6, and correspond to 18 consonants. Vowels are ignored, as are the letters W, H and Y. The basic chart looks like this:
1: B, F, P, V
2: C, S, K, G, J, Q, X, Z
3: D, T
5: M, N
The Soundex code for Marshall would start with the letter M. Ignoring the "a", the next letter would be "r" which codes to 6. The "s" after the "r" codes to 2, and ignoring the "h" and the second "a" leaves "l" or 4, which makes the Soundex code for Marshall M-624.
Any surname that does not have enough consonants for three digits is given zeroes for numbers. The popular example is "Lee", which would simply be L-000. Double letters (Like in "Allen", for example) are counted as one letter. NARA lists other special rules and exceptions for surnames with prefixes, Native American names, and other non-English names on their website at National Archives And Records Administration.
The easiest method, however, is to use one of the many Soundex code generators available online. Keep in mind that you may have to generate several different codes for one surname. Although the advantage of Soundex is that it groups similar-sounding names together, it's not a perfect system. If you're looking for a "Knutson" or a "Knowles" for example, you should find the Soundex code for the name both with and without the silent K.
There was also a discrepancy from Soundex coders who treated consonants with the same code around the letters W and H as double letters. The standard example used is "Ashcraft"; one coder may have Soundexed the name as A-226 (A + 2=S + 2=C + 6=R) while another may have come up with A-261 (A + 2=for both the C and S on either side of the H + 6=R + 1=F)
What do I do with my Soundex codes?
Information indexed by Soundex was written on cards; these cards were later microfilmed. The University of Delaware library advises that the 1880 census microfilms are separated by state or territory. "After coding a surname, therefore, researchers must know or speculate where a family, person, or institution was located in 1880," they write on their website.
The University of Delaware library also suggests you know the first name of the head of the family, and information such as age, specific location or birthplace. These clues will also come in handy as you comb through your Soundex code of the person for whom you are looking. Remember that many different surnames can share the same Soundex code – looking through M-624 will include not only Marshall, but Markel, Merkel, and Marcelus, for example. The correct microfilmed Soundex card will tell you where to look for the complete entry you need.
Who uses Soundex anymore and why bother to learn?
The WPA (Works Progress Administration) Soundex census projects ended as World War II started demanding workers. The 1930 census, the last to be Soundexed , has only 11 states Soundexed completely: Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi, North Carolina, South Carolina, Tennessee, and Virginia. Certain counties in Kentucky and West Virginia also had Soundex cards prepared.
Today, the Soundex underlies many of the genealogy databases you use, which may leave you wondering why you should learn it when the computer can do it for you. But Soundex has also been used by other archives in the past, and not all of them can be searched with the click of a mouse. Think of knowing how to use Soundex as you would knowing how to do long division by hand -- you might not always need it, but when there's no other way to figure it out, you'll be glad you've got the skill.