Genealogists often encounter mysterious notations, abbreviations, or numeric/letter codes on United States Census Population Schedules from 1920, 1930, 1940, and 1950. These codes could have originated from Census Bureau workers in post-enumeration processing, might reflect the enumerator’s own tallying methods, or could be official notation from enumerator instructions. Understanding these codes will help you glean more context about your ancestors and the data collection process itself.
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IntroductionIntroduction
As you peruse historical census records in your genealogical research, you might come across peculiar codes in margins, columns, or near the enumerated entries. These codes can be baffling at first glance—some appear as letters and numbers scrawled in pencil; others might be typed in or stamped.
The good news is that many of these codes do have documented explanations. By learning how and why they were used, you can:
- Validate or clarify the information provided (e.g., citizenship, occupation, education).
- Gain insight into data categorization for statistical purposes (e.g., race, industry codes).
- Learn which codes are purely clerical or administrative, and which codes provide genealogically relevant details.
Below you’ll find a step-by-step approach to identifying and deciphering these codes for each major census year—1920, 1930, 1940, and 1950.
The History of United States Census CodesThe History of United States Census Codes
So how did coding of US Census data get started and why? By 1870 and with a population of over 38 million, the Census Bureau realized that counting and tabulating results by hand could now longer be sustainable and effective. A rudimentary device created by Charles W. Seaton, a United States Census Bureau supervisor was first used in 1872. For the 1880 US Census, with over 50 million residents in the United States, the tabulation still required seven years to finish!
The Hollerith Tabulating MachineThe Hollerith Tabulating Machine
- Herman Hollerith, a former US Census employee, created a tabulation machine that not only would prove much more effective than earlier machines, but also lead to the creation of the International Business Machine (IBM) corporation. Hollerith’s machine utilized “punch cards” to code the census and then tabulate results. For the 1890 census, which showed a 25% increased over population compared to 1880 with 63 million residents, a fleet of Hollerith machines was used for tabulation. The results were finished months ahead of schedule and way under budget.
The Univac I ComputerThe Univac I Computer
- The newly created Univac I computer was utilized to code and tabulate results of the 1950 US Census, again using punch cards. With a population of over 150 million, the Univac I could process 4,000 items per minute.
Why Were Codes Used?Why Were Codes Used?
Enumerator’s Own Tallying Enumerator’s Own Tallying
Some enumerators made ticks or shorthand notes to keep track of specific data—like how many heads of household they had enumerated, how many farms, or simply to ensure no household was missed.
Census Bureau Coding Census Bureau Coding
After enumeration, the Census Bureau employed clerks (or used mechanical tabulating equipment) to tabulate national statistics. These workers added alphanumeric or numeric “coding” to standardize responses for:
- Occupation and Industry: A code that classifies an individual’s occupation (e.g., machinist, farmer, teacher) and industry (e.g., automobile factory, farm, public school).
- Nativity and Citizenship: Codes for “citizen,” “naturalized,” “alien,” etc.
- Race and Ethnicity: Sometimes coded for internal tabulation.
Official Enumerator Instructions Official Enumerator Instructions
Enumerator instruction manuals sometimes included shorthand notations. For example, enumerators might mark “Ab” for absent individuals, or use notations such as “H” for head, “W” for wife, and so forth. While these abbreviations are generally self-evident, they sometimes differ by year and location.
General Approach to Deciphering Census CodesGeneral Approach to Deciphering Census Codes
- Check the Census Form & Instructions: Start with the official forms and enumerator instructions published by the Census Bureau for that specific year. They often explain the official codes (column headings, official abbreviations) you’ll see on the form itself.
- Look for Patterns & Consistency: If you see a repeated set of pencil notations (e.g., “11” or “F” in the margin) next to multiple entries, that pattern might indicate a category like “Farm” (F) or a certain occupation code (11). Consistency across multiple pages can be a clue.
- Consult Reference Guides: For 1940 and 1950 censuses especially, the Census Bureau used extensive numeric coding for occupation and industry. These official code lists are sometimes available through the National Archives or genealogical websites.
- Correlate with Known Data: If a family member’s occupation was known to be “laborer in a steel mill,” find how that might correlate with a numeric occupation code in that year’s official reference.
- Ask the Community: Genealogical forums, historical societies, or local archives often have compiled lists of enumerator and coding abbreviations relevant to a particular locale.
Deciphering Codes by DecadeDeciphering Codes by Decade
1920 Census Codes1920 Census Codes
Key Official Columns to WatchKey Official Columns to Watch
- Place of birth (including state or foreign country).
- Citizenship status: “Na” (Naturalized), “Pa” (First Papers), “Al” (Alien).
- Mother tongue (for foreign-born individuals).
Enumerator Tick Marks Enumerator Tick Marks
- Sometimes you’ll see small tally marks in the left margin indicating how many dwellings were enumerated or how many heads of household were recorded so far in the Enumeration District (E.D.). These typically have little genealogical meaning but confirm the enumerator’s personal counting system.
Clerical or Post-Enumeration Codes Clerical or Post-Enumeration Codes
- In some cases, you might see red or blue pencil codes in the occupation or nativity columns—these often correspond to internal Census Bureau codes used for punching the data cards. If you see a consistent numeric code like “82” for multiple “Farmers,” consult known occupation code lists from the 1920 era.
Where to Find More InfoWhere to Find More Info
- Check the 1920 Enumerator’s Instruction Manual (available online at some genealogical or archival websites).
- Look at reference works like the National Archives microfilm publication T625 (which includes official forms and instructions).
1930 Census Codes1930 Census Codes
Employment & Industry CodesEmployment & Industry Codes
- By 1930, the Census Bureau started refining its occupation and industry coding system. Enumerators typically wrote out the occupation, but post-enumeration coders (at the Bureau) might have written numeric or letter codes in the far right margins.
Race & Nativity Notations Race & Nativity Notations
- Codes for race (e.g., “W” for White, “Neg” or “B” for Black, “Mex” for Mexican, “Ch” for Chinese, etc.) appear as typed or written abbreviations. In some enumerations, you might see numeric codes too—these are for internal classification.
Citizenship Status & Year of Immigration Citizenship Status & Year of Immigration
- Markings in the columns for “Naturalized or Alien” can be accompanied by notations referencing the year of immigration or a code for partial processing (e.g., “Pa”).
Local Tally Marks Local Tally Marks
- Enumerators might have circled or underlined the “Head” of household or used a quick symbol such as “#” to differentiate families.
Where to Find More Info Where to Find More Info
- 1930 Census Enumeration Instructions (available through the National Archives).
- Genealogy library collections or websites often host digitized enumerator instruction pamphlets.
1940 Census Codes1940 Census Codes
Expanded Coding for Occupation & Industry Expanded Coding for Occupation & Industry
- The 1940 census introduced an even more complex code structure.[1] You might see numbers like “V1941,” “339-51,” or other multi-digit references. These reference standardized occupation codes (e.g., 339) and industry codes (e.g., 51).
- The format often involves a three-digit occupation code and a two-digit industry code, sometimes separated by a dash or space.
Supplementary Questions & Codes Supplementary Questions & Codes
- On some lines (sample lines), enumerators collected additional information about parents’ birthplaces, language spoken in childhood, or Social Security details. If you see codes in these columns, they may be referencing internal tabulation categories (e.g., “N1” for No Social Security number, “Ot” for other forms of coverage).
Marital Status / Age at First MarriageMarital Status / Age at First Marriage
- Shorthand notations like “M1,” “M2,” etc., are sometimes used to denote first, second marriage. But often these are enumerator abbreviations rather than official codes.
Internal Coding by the Census BureauInternal Coding by the Census Bureau
- After the census was collected, special coders (often in large coding centers) annotated schedules with numeric codes in pencil or colored ink. Occupation is usually coded in columns 26-28, while industry codes appear in columns 29-31 (the exact columns depend on the form layout).
Where to Find More InfoWhere to Find More Info
The 1940 Census Enumerator’s Reference Manual and Occupation & Industry Coding Manuals (available via the National Archives and genealogical databases).
Look for the published “United States Census Bureau Coding Instructions” for 1940 in genealogical libraries.
1950 Census Codes1950 Census Codes
Sample Lines & Extra Questions Sample Lines & Extra Questions
- The 1950 census introduced more “sample lines,” where every fifth person (or so) might have been asked additional questions. Codes or margin notes in these sections could denote question types, classification categories (e.g., farm vs. non-farm), or placeholders for deeper data.
Occupation & Industry Codes Occupation & Industry Codes
- Like 1940, 1950 used standardized numeric codes for occupation and industry. You may notice a similar multi-digit system. For example, “210” might represent a “Farm laborer,” while “272” might be “Clerical worker” in a certain industry.
Residency Notations Residency Notations
- Additional notations regarding whether the individual lived on a farm or in a city could appear as “R” (rural) or “U” (urban), or numeric codes linking to metropolitan or non-metropolitan categories.
Household Tally Marks Household Tally Marks
- Some enumerators continued to track the total number of enumerated households per block or E.D. with brief margin notes—e.g., “HH 25” or “Cum 75” (cumulative total). These often have no genealogical data, but confirm enumerator progress.
Where to Find More Info Where to Find More Info
- 1950 Census Enumerator’s Instructions (some portions are available online; full official copies reside in the National Archives).
- 1950 Census of Population: Classification of Occupations” (Census Bureau publication) can help decode occupation and industry codes.
Practical Tips & Techniques for GenealogistsPractical Tips & Techniques for Genealogists
Download or Access the Enumerator Instructions Download or Access the Enumerator Instructions
- For each census year, the Census Bureau released instructions to enumerators. These can often be found digitized in major genealogy websites, the National Archives, or through genealogical societies.
Use Occupation & Industry Code Guides Use Occupation & Industry Code Guides
- For 1940 and 1950, several genealogical and academic websites have compiled tables cross-referencing the numeric codes to specific job titles and industries. Matching a code with a job title can confirm or clarify family stories about employment.
Check Local Historical/Genealogical SocietiesCheck Local Historical/Genealogical Societies
- Some areas had unique or pilot coding methods, especially for smaller enumerations (like certain U.S. territories). Local historians may have deciphered these region-specific codes.
Compare Multiple Family Records Compare Multiple Family Records
- If you’re unsure of what a code means, see if it appears across multiple families with similar traits (same occupation, same race, or same immigration status). The pattern might clarify the meaning.
Don’t Overinterpret Non-Standard Jottings Don’t Overinterpret Non-Standard Jottings
- Many margin notes were simply enumerator or supervisor reminders that do not necessarily affect genealogical data. If a code doesn’t align with official instructions or tabulation coding manuals, it might just be a personal notation.
Consult the National Archives Catalog & Finding Aids Consult the National Archives Catalog & Finding Aids
- The National Archives provides extensive documentation, microfilm publications, and occasionally code manuals for each census year.
Example: Decoding an Occupation Code in 1940Example: Decoding an Occupation Code in 1940
Suppose you see “859-43” in faint pencil next to your ancestor’s name in the occupation column. By referencing a 1940 Occupation & Industry Code Manual, you may learn that “859” designates “Sewing Machine Operator” and “43” designates the “Apparel Manufacturing” industry. That insight can corroborate family lore about a relative who worked in a clothing factory, thereby building confidence in your genealogical narrative.
ConclusionConclusion
Deciphering the various codes on the 1920, 1930, 1940, and 1950 U.S. Census Population Schedules can unlock deeper insights into your ancestors’ lives, occupations, and communities. While some notations are purely administrative or clerical, others provide clues about the official data classification systems for occupation, citizenship, and more. By consulting enumerator instruction manuals, referencing official code lists, and engaging with genealogical communities, you can skillfully interpret these mysterious marks and enrich your family history research.
Always cross-reference the codes you find with known instruction manuals or code references for the specific census year. Doing so ensures you gather the most accurate and meaningful information about your ancestors from these invaluable historical records.
See alsoSee also
Explore more about United States census codesExplore more about United States census codes
- U.S. Census records collection at MyHeritage
- Census Tick Marks and Codes--Revisited Yet Again! – Elizabeth Shown Mills
- Deciphering Codes Appended to 1910 to 1950 Census in One Step -– Steve Morse One-Step Site
- Enumeration Forms: Questions and Instructions – IPUMS
- Enumerator Instructions – United States Census Bureau
- Tabulating and Processing – United States Census Bureau
References
- ↑ Stephen P. Morse, PhD; Joel D. Weintraub, PhD. Deciphering Miscellaneous Codes Appended to the 1940 Census in One Step