A nationwide population census on a regular basis dates from the establishment of the United States. Article I, section 2, of the United States Constitution requires that

Representatives and direct Taxes shall be apportioned among the several States which may be included within this Union, according to their respective Numbers. . . . The actual Enumeration shall be made within three Years after the first Meeting of the Congress of the United States, and within every subsequent Term of ten Years, in such Manner as they shall by Law direct.

The first enumeration began on the first Monday in August 1790, less than a year after the inauguration of President Washington and the assembling of the first Congress of the United States. Responsibility for the 1790 census was assigned to the marshals of the U.S. judicial districts under an act which, with minor modifications and extensions, governed the taking of the censuses through 1840. The law required that the completed schedules of the census be posted in two of the most public places within each jurisdiction, "there to remain for the inspection of all concerned. . ." and that "the aggregate amount of each description of persons" for every district be transmitted to the President. The inquiries in 1790 related to six items and called for the name of the head of the family and the number of persons in each household of the following descriptions: Free White males of 16 years and upward, free White males under 16 years, free White females, all other free persons, and slaves.

Starting with the 1800 census, the enumeration was carried out under the direction of the Secretary of State, and, from 1800 to 1840, the marshals reported the results to him.

The 1800 and 1810 population censuses were similar in scope and method to the 1790 census. However, members of Congress, as well as statisticians and other scholars both within and outside the Federal Government, urged that, while the population was being canvassed, other information needed by the new Government should be collected. The first inquiries on manufacturing were made in 1810, and, in later decades, censuses of agriculture, mining, governments, religious bodies, business, housing, and transportation were added. (Legislation enacted in 1957 and later years provided for the economic, government, and agricultural censuses to be taken at times that do not conflict with those in which the population and housing censuses are conducted.)

The census of 1820 covered the subject of population in somewhat greater detail than the preceding one. This census is notable for having obtained, for the first time, the numbers of the population engaged in agriculture, commerce, and manufacturing.

The census of 1830 related solely to population, but its scope concerning this subject was substantially extended. The use of uniform printed schedules began with this census. In previous censuses, the marshals or their assistants had used

whatever paper they had, ruled it, written in the headings, and bound the sheets together.

The census act for 1840 authorized the establishment of a centralized census office during each enumeration and provided for the collection of statistics pertaining to "the pursuits, industry, education, and resources of the country." The new population inquiries included school attendance, illiteracy, and occupation.

Through the census of 1840, the household, rather than the individual, was the unit of enumeration in the population census, and only the names of the household heads appeared on the schedules. There was no tabulation beyond the simple addition of the entries submitted by the marshals, and there was no attempt to publish details uniformly by cities and towns or to summarize returns for each State, by county, unless the marshals had done so.

The act which governed the taking of the seventh, eighth, and ninth decennial censuses (1850-1870) provided for several changes in census procedures: Each marshal was responsible for subdividing his district for reporting purposes into “known civil divisions," such as counties, townships, or wards, and for checking to ensure that the returns of his assistants were properly completed. The number of population inquiries was expanded, every person's name was to be listed, and the items related to each individual enumerated. Additional "social statistics" (information relating to taxes, schools, crime, wages, value of estate, etc.) and data on mortality were collected for the first time in 1850.

A noteworthy feature of the 1870 census was the introduction of a rudimentary tabulating machine in the latter part of 1872 for use in the closing months of data processing. Another innovation was the employment of maps, charts, and diagrams to graphically present the most significant facts of the enumeration.

The general scope of the 1880 census was expanded only slightly over that of the 1870 census, but much greater detail was obtained for many of the items. The census act for 1880 provided for the establishment of a census office in the Department of the Interior and the appointment, by the President, of a superintendent of the census for the duration of the census. An important change for the 1880 census was the use of specially appointed supervisors and enumerators in place of the marshals and their assistants. Each supervisor was required to propose to the superintendent appropriate subdivisions of his district and recommend suitable persons to work as census takers.

Another provision of the 1880 census act was that, for the first time, enumerators were forbidden to disclose census information. From the time of the first census in 1790, some people had regarded many of the questions as an invasion of privacy, but there was no law limiting the extent to which information on any schedule could be used or seen by the public. (Subsequent demographic and economic censuses, as well as most surveys, were carried out according to statutes

that made compliance mandatory, with penalties for refusal, and responses confidential, with penalties for disclosure. These laws were codified by Congress in 1954 as Title 13, U.S. Code.)

Again, in 1890, there was a slight extension of the scope of the decennial census, and some subjects were covered in even greater detail than in 1880. Data were collected in supplemental surveys on farm and home mortgages and on the indebtedness of private corporations and individuals. The census of 1890 also provided, for the first time in the history of the census, a separate schedule for each family. A distinguishing feature of this census was the introduction of punchcards and electric tabulating machines for processing the data.

The 1900 census was limited to those questions asked for all the population in 1890, with only minor changes in

content.

From the 1840 census through census of 1900, a temporary census office had been established before each decennial census and disbanded after the census had been taken and the results compiled and published. A permanent Bureau of the Census was established in 1902, and the census of 1910 was the first to be taken by this organization. One important feature of this census was the method by which temporary employees were selected. Since 1880, both supervisors and enumerators had been appointed by Congress; appointees were given noncompetitive examinations to determine whether or not they had the ability to fulfill their duties. In 1910, prospective census employees were given open competitive examinations administered throughout the country.

The 1910 decennial census was also notable for the method of presenting the results. Those statistics which were ready first, and especially those which were in greatest demand (such as the total population of individual cities and States, and of the United States, as a whole), were distributed first in the form of press releases. Later, they were presented in greater detail in the form of official bulletins, and then in an abstract with State supplements, appearing in this form 6 months to a year before the final reports were issued.

In 1920, and also in 1930, there were certain improvements in collection methods and minor changes in the scope of the census. A census of unemployment was conducted in 1930 in conjunction with the decennial census; data were collected for each person reported to have a gainful occupation but who was not at work on the working day preceding the enumerator's visit.

The 1940 census was, in many ways, the first contemporary census. One of the major innovations was the use of advanced statistical techniques, such as sampling, in census procedures. Previously, such techniques had only been tried experimentally. Sampling allowed the addition of a number of questions without unduly increasing the burden on respondents and on data processing. The introduction of sampling in the 1940 census also made possible the publication of preliminary returns fully 8 months in advance of complete tabulations. The Bureau was able to increase the number of detail tables published and to review the quality of the data processing with more efficiency.

Reflecting the concerns of the Depression years, the Bureau asked several questions in 1940 that measured employment and unemployment, internal migration, and income. The 1940

census was the first to include a census of housing; this obtained a variety of facts on the general conditions of the Nation's housing and the need for public housing programs. (Prior to this first census of housing, the housing data collected as part of the population censuses were generally limited to one or two items.)

At the time of the 1950 census, a survey of residential financing was conducted as a related, but separate, operation, with information collected on a sample basis from owners of owner-occupied and rental properties and mortgage lenders. Similar surveys were conducted in conjunction with the 1960, 1970, and 1980 censuses. (The inquiries in these surveys are not included in this publication; see references 4, 6, 8, and 9 in the bibliography, p. 91).

Most population and housing inquiries included in the 1940 census were repeated in the subsequent censuses, and a few were added, for example, place of work and means of transportation to work (1960), occupation 5 years before the census (1970), and housing costs (1980). In 1940 and 1950. the sample population questions were asked only for those persons whose names fell on the sample lines of the schedule. Sampling was first used for the housing schedule in 1950, with a few questions asked on a cyclic basis: There was one pair of sample questions for household 1, another pair for household 2, etc., until household 6, when the cycle was started again with the first pair of questions. In the 1960 census, the sampling pattern was changed for population and housing questions alike: If a housing unit were in the sample, all the household members were also in the sample. The only population questions on a 100-percent basis (name and address, age, sex, color or race, marital status, and relationship to head of household) were those necessary to identify the population and avoid duplication.

The major innovation of the 1950 census was the use of an electronic computer, the first of a series, which was delivered to the Bureau of the Census in 1951 to help tabulate some of the data from the census of 1950.

Nearly all of the data processing was done by computer in the 1960 census. An electronic device for "reading" the census schedules was a further innovation. Special schedules were designed on which the answers could be indicated by marking small circles, and the information recorded in this manner could be read by the FOSDIC (film optical sensing device for input to computer) rather than by a clerk preparing punchcards. In actual practice, the schedules were first microfilmed. and then the FOSDIC scanned the microfilm copy. From the position of the marks on the schedule, the information was converted into magnetized spots on tape, which was then processed by electronic computers.

The 1960 census was also the first in which the mails were used extensively to collect population and housing data. The field canvass was preceded by delivery to every occupied housing unit of a questionnaire which contained the 100-percent questions (those asked for all persons and housing units). Householders were asked to complete the questionnaire and hold it until an enumerator called. The sample items were on a different questionnaire: In urban areas containing about 80 percent of the Nation's population, the enumerator left a

questionnaire containing the sample population and housing. questions at every fourth household and requested the respondent to fill it out and mail it to the census district office. (Self-enumeration had been used on a very limited scale previously, but this was the first time it was made a major part of the decennial procedure.) When these questionnaires were received in the district office, the responses were transcribed to the special FOSDIC schedules. In rural areas, the sample information was obtained from every fourth household at the time of the enumerator's visit and recorded directly on the FOSDIC schedules.

An addition to the 1960 decennial program was the Survey of Components of Change, which measured the quantitative and qualitative impact of basic changes that occurred in the Nation's housing stock during the decade 1950-1960. The survey also provided a measure of "same" units, i.e., the preponderant part of the housing inventory which was not affected by the basic changes. The first survey of this type had been conducted in 1956 as a key part of the National Housing Inventory. Similar surveys were conducted in conjunction with the 1970 and 1980 censuses. (The inquiries in these surveys are not included in this publication; see references 6, 8, and 9 in the bibliography, p. 91.) The 1970 census marked the use every where of separate, FOSDIC-readable household questionnaires approximately 70 million of them-rather than the large schedules that contained information for four or more households. Thus, respondents could mark the appropriate answer circles on their questionnaires, which could then be processed directly without transcription.

The mails were used even more extensively in the 1970 and 1980 censuses than in 1960. Approximately 60 percent of the population in 1970 (essentially that in large metropolitan areas), and 90 percent in 1980, received questionnaires by mail and were asked to complete and mail them back to the census district office. These questionnaires contained the 100-percent and, where appropriate, sample questions. In the areas where this procedure was used, enumerators contacted only those households that had not returned questionnaires or had given incomplete or inconsistent answers. For the remainder of the population, most of which was located in rural areas or small towns, letter carriers left a census form containing the

100-percent questions at each residential housing unit on their routes. An enumerator visited each of these households to collect the completed questionnaires and ask the additional questions for any household in the sample. There was a supplemental questionnaire that enumerators used on Indian reservations in 1980 to collect additional information about households with one or more American Indian residents.

In the 1970 census, the only population data collected on a 100-percent basis related to the same five subjects that had been collected on a 100-percent basis in 1960. Most sample questions were asked of either a 15-percent or a 5-percent sample of households, but some were asked for both, thus constituting a 20-percent sample. Only 15 housing items were asked on a complete-count basis; the remaining items were asked on a sample basis similar to that used for the population inquiries. Changes in content over 1960 were relatively minor. The pattern for 1980 was similar, except that the question of Spanish origin (a 5-percent item in 1970) was asked at all households, and there was only one set of sample questions. The sample, however, was used at every other household (50 percent) in places of less than 2,500 inhabitants and at every sixth household (17 percent) elsewhere. This allowed the publication of greater and more reliable detail for small geographic areas.

For 1970, extensive discussions with census data users led to a major increase in the amount of statistics to be tabulated, especially for small areas. As part of the 1970 census program, the Bureau published data for each of 1.5 million city blocks (including all blocks in urbanized areas), as compared with 1960, when the Bureau provided data for the 750,000 blocks within the city limits of places of 50,000 or more. For 1980, there were data for 1.8 million blocks, with the population limit lowered to include incorporated places of 10,000 or more inhabitants.

The 1970 and 1980 population and housing census data are published in a series of reports similar to those issued after the 1960 census. In addition, computer summary tapes, containing much more detail than appears in the printed reports, are made available for sale to the many users with access to electronic data processing equipment.

The following chart indicates the decennial population schedules from 1790 through 1900 that exist and are available on microfilm for public use at the National Archives and its regional centers and at libraries in various parts of the country. (Microfilm reels may also be purchased or borrowed on interlibrary loan from the National Archives, which periodically publishes a catalog for use in ordering.2)

All decennial census schedules are arranged geographically. There are federally prepared indexes to the 1880, 1890, and 1900 censuses on microfilm; local indexes for other years have been compiled and published by various organizations or individuals. Libraries and genealogical collections should be consulted for these.

'National Archives and Records Service. Federal Population and Mortality Schedules, 1790-1890, in the National Archives and the States. Special List No. 24, Washington, D.C., 1971. 89 pp.

2 Id., Federal Population Censuses, 1790-1890. A catalog of microfilm copies of the schedules. Washington, D.C., 1977, 90 pp. Also, 1900 Federal Population Census, A Catalog of Microfilm Copies of the Schedules. Washington, D.C., 1978. 84 pp.

Most of the 1890 records were so badly damaged by fire in January 1921 that only fragments of the population schedules remain. These are for a few isolated counties and several streets in Washington, D.C. A number of the special schedules of Union veterans of the Civil War and their widows were saved, however, including those for U.S. vessels and Navy yards.

Schedules and questionnaires from the 1910 and subsequent censuses are confidential, by law, for 72 years and cannot be released to anyone except the named individuals, their heirs (on proof of death), or their legal representatives. Applications for transcripts should be made to the Census Bureau.

Beginning with the 1880 census, enumerators were provided with maps of their assigned areas. In the absence of a street address these maps, which are in the custody of the National Archives, are frequently helpful in locating particular entries on census schedules.3

3 Id.. Preliminary Inventories. Number 103. Cartographic Records of the Bureau of the Census. Washington, D.C., 1958. 108 pp.