Soundex

United States

U.S. Census

Soundex

The Russell Soundex (a.k.a. American Soundex, and Miracode) and its usefulness to genealogists are explained, some online Soundex converters listed, and rules given for how to manually create a Soundex code.

1910 U.S. federal census Soundex family card

1910 U.S. federal census Miracode for 4 households

Introduction

Soundex is a phonetic index that groups together names that sound alike but are spelled differently, for example, Stewart and Stuart. This helps searchers find names that are spelled differently than originally expected, a relatively common genealogical research problem.

The indexing system was developed by Robert C. Russell and Margaret K. Odell. It was patented in 1918, reissued 1923, and 1922. It is formally called the Russell Soundex, and a variation used on the censuses is called the American Soundex. When a computer was used to generate a Soundex index card for a census it was called a Miracode, and the information listed was slightly different from handwritten Soundex cards for the same census.

The most well-known genealogical use of Soundex is on parts of the 1880, 1900, 1910, 1920, and 1930 United States federal censuses. It is also used by the federal government for selected ship passenger arrival lists, certain Canadian border crossings, and some naturalization records. A few county governments have also used a version of Soundex for courthouse kinds of records. More recently, Ancestry.com and other Internet companies have featured a Soundex search for their online databases. Many non-genealogical search engine algorithms borrow heavily from concepts first introduced by Soundex.

How the Soundex Works

The Soundex is based on the classification of letters of the alphabet (consonants) into six sound-alike key letter groups. For example, in many languages the B and V sounds are nearly interchangeable; as are B and P; and V and F. So the first phonetic group of key letter consonants is B, F, P, V. Vowels are fluid and disregarded, as are H and W. By giving the same value to key letter consonants that often sound alike, the index brings names together that would usually be pronounced alike with little regard to their actual spelling. Each sound-alike group of key letter consonants is assigned a number. Each family name is assigned a Soundex code that has the initial letter of the name followed by exactly three of the sound-alike key letter group numbers. For example, Stewart = S363 and Stuart = S363.

Modern online search engines that use Soundex do it without displaying the Soundex codes—similar names spelled differently simply appear together on the search results list. But from time to time a researcher may need to understand Soundex codes in order to use one of the older Soundex indexes on microfilm.

Soundex Rules

Follow these rules to manually create a Soundex code for an ancestor’s name.

Basic Rules

• Every soundex code consists of a letter and three numbers, such as D432.
• The letter is always the first letter of the name. For example, Clausen = C425, and Klausen = K425.
• After the first letter, disregard all vowels a, e, i, o, u, and y, and the consonants h and w.
• Numbers are assigned to the remaining letters of the name according to the table Soundex Key Letter Codes below.
• Zeroes are added at the end if necessary to produce a four-character code. Excess letters are disregarded if they would produce a code longer than four-characters. For example Lee = L000, and Christopherson = C623.

Soundex Key Letter Codes

Number	Letters Represented
1	b, f, p, v
2	c, g, j, k, q, s, x, z
3	d, t
4	l
5	m, n
6	r

Additional Rules

• Double key letters should be treated as one letter. For example, Gutierrez = G362.
• Side-by-side letters with the same code number should be treated as one letter. For example, Campbell = C514, and Jackson = J250, and Pfister = P236.
• Vowel key letter seperators. If a vowel (a, e, i, o, u, y) separates key letters that have the same code number, those key letters should be treated as two letters. For example, Tomzak = T522, and Roses = R220.
• H or W key letter seperators. If an h or w separates key letters that have the same code number, those key letters should be treated as one letter. For example, Ashcroft = A261, and Carwruth = C630.
• Names with prefixes, such as Van, Con, De, Di, La, or Le, are coded both with and without the prefix because the name might be listed under either code. Note, however, that Mc and Mac are not considered prefixes. For example, Van Deusen = V532 or D250.

Additional Examples

These examples are taken from Guide to Genealogical Research in the National Archives, page 22.

Name	Code		Name	Code		Name	Code		Name	Code
Allricht	A462		Kavanagh	K152		McGee	M200		Schafer	S160
Eberhard	E166		Lind	L530		O'Brien	O165		Shaeffer	S160
Hanselmann	H524		Lukaschowsky	L222		Oppenheimer	O155		Zita	Z300
Heimbach	H512		McDonnell	M235		Riedemanas	R355		Zitzmeinn	Z325

Online Soundex Converters

The easiest way to obtain the Soundex code for a name is to use one of several online Soundex converter programs. Simply type a name, and at the click of a button, the converter will divulge the corresponding Soundex code. There may be subtle differences between programs.

• SoundEx Converter Form
• Yet Another Soundex Converter

Limitations

There are three limitations to the Soundex system researchers should be aware of.

1. Indexing rules were not always followed consistently. The government indexers may have occasionally overlooked some of the fine points of the additional indexing rules. If you cannot find a name under the correct code, try looking under the code as if the additional rules were overlooked. For example, try looking for Ashcroft under both A226 and A261, or try looking for Pfister under both P236 and P123.
2. Unrelated names may be grouped together. Sometimes names that do not appear to be related show up together on a Soundex index. Ignore clearly unrelated names. For example, if you were looking for Wilkins, you may also find under the same Soundex code W425, the name Walakynowski.
3. Related names may not be grouped together. Sometimes names that are obviously related do not come together in the same Soundex index group. For example, Clausen is under C425 and Klausen under K425. If you cannot find a name you seek in a Soundex index, there are 20 alternative ideas in the Wiki article Guessing a Name Variation to help find elusive names in indexes.

Limited Data

One of the most well-known uses of Soundex indexes is for some of the federal censuses of the United States. More recently, these old microfilm indexes have been largely replaced by online search engines. If you ever have an occasion to use a census Soundex on microfilm, keep in mind that the Soundex card is only a summary. It does not show as much information as the original census schedule.

Sample Images

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  Sample 1930 Soundex index cards

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  Half page of the 1930 Federal census of Bronx, New York

Related Websites

• The National Archives, Soundex System
• Gary Mokotoff, Soundexing and Genealogy
• Rick Parsons, Soundex - the True Story

Related FamilySearch Research Wiki Articles

• United States Census Indexes
• Finding a Person in the 1930 Census (Even Without An Index)