The Soundex code represents a word, such as a person's name, based on the way
the word sounds rather than the way it is spelled. Words that are spelled
differently but sound the same such as Stewart and Stuart have the same Soundex
code. This was sometime called a Miracode when a computer generated the code.
The National Archives uses the Soundex system to index most of the census
records from 1880 to 1930 and some of the passenger arrivals records. When
these records were originally written many of the Americans were illiterate and
did not know how to write their own last name. They would pronounce their name
and the person writing the record would spell it according to how it sounded
and often incorrectly.
Thus, the spelling of names varies in early records but these variations are
phonetically identical and they have identical Soundex codes.
Soundex Coding Rules
1. Every Soundex code consists of a letter followed by three digits, such as
2. The letter is always the first letter of the word being coded.
3. After the first letter disregard the letters A, E, H, I, O, U, Y and W.
4. Digits represent the remaining consonants according to the chart below.
5. If the resulting code is less than four characters zeros are add at the end.
6. Excess letters are ignored if they would produce a code longer that four
|Soundex Letter Codes
|| Represents the Letter
|| B, F, P or V
|| C, G, J, K, Q, S, X or Z
|| D or T
|| M or N
Additional Soundex Rules
1. Adjacent Letters. Side by side letters with the same Soundex letter
code number are treated as one letter. Jackson is coded: J250. (J, plus 2 for
C, K is ignored, S is ignored, 5 for N, 0 added).
2. H or W Letters Separator. Letters separated by an h or w and with
the same Soundex letter code are treated as one letter. Ashcraft is coded:
A261. (A, plus 2 for S, C is ignored, 6 for R, 1 for F).
3. Vowel Letter Separator. Letters separated by a vowel (a, e, i, o, u,
y) are both coded.
4. Name Prefix. Name prefixes such as Con, De, Di, La, Le or Van are
not coded. Prefixes Mc and Mac are included in the code. Note: Coders sometimes
missed this rule and a surname could be coded with or without the prefix. A
through search should include the code from both forms.