Illinois’ first census

Census Workers in 1960.
Photo from the Abraham Lincoln Presidential Library & Museum. 
Two hundred years ago, Illinois participated in its first decennial census as one of the nation’s 24 states. Completed on the first Monday in August of 1820, it produced the first official snapshot of Illinois’ demographics as a state.

The Census was authorized by Article I, Section 2 of the Constitution, with the instruction that it take place “within three Years after the first Meeting of the Congress,” which worked out to 1790, “and within every subsequent Term of ten Years.” It was originally spelled out in the Constitution as being necessary for the purposes of apportionment of seats in the population-based House of Representatives. With Illinois attaining statehood in 1818, its first census as a state would be conducted in 1820.

Not surprisingly, the nation’s fourth decennial census was conducted much differently than this year’s enumeration. For one thing, it was a nationwide, in-person count of the entire population. That is: a census taker physically traveled to every single dwelling in the nation and interviewed every resident or head of household. When it was completed, the census takers had compiled a population of 9,625,734 persons in each of the states, plus the Michigan and Arkansas Territories and the District of Columbia.

Federal marshals were issued their instructions by Secretary of State John Quincy Adams. They then deputized the individuals who would travel the nation doing the actual enumeration. By the time the task was completed, the State Department was able to assemble the count and the statistics for each state and county in the nation, and could, among other things, rank the states in order of population.

Illinois came in dead last.

The 55,211 Illinoisans (the approximate population of the villages of Oak Lawn or Mount Prospect today) counted in the 1820 Census lived in each of the state’s 19 counties. Even Missouri, which had just joined the union at the time of the census, had a larger population than Illinois. The nation’s largest state that year was New York at 1,372,812, slightly less than today’s combined population of DuPage and Kane Counties. Only Virginia and Pennsylvania joined New York in having more than 1 million residents.

The 1820 Census sought to determine more than just the numerical population of the nation and its states. It counted both free and enslaved persons, as well as those who were not citizens of the United States. It also calculated the ages of each person and the occupations of those in the workforce, splitting it among the “number of persons engaged in Agriculture,” as well as “Commerce” and “Manufacture.”

Illinois’ largest demographic group that year was white males under ten years: a total of 10,554. The second largest group the census found was the 9,558 white females under ten. In an era of much shorter life expectancy, the census found approximately one-fifth as many people over age 45 as under age 10, across all groups. The census also found 917 enslaved persons living in Illinois, with the largest subgroup of these being males aged 10 to 16: a total of 179.

Illinois has always been an agricultural state, and this was decidedly true in 1820. Of the three categories of employment identified by the census, agriculture was by far Illinois’ leader: 12,395 persons were engaged in agriculture. Though this segment of the economy was the overwhelming leader in Illinois, the state ranked last in the nation in persons engaged in agriculture, coming in just 200 behind the next closest state, Rhode Island. In 1820, 233 Illinoisans were reported engaged in commerce and 1007 in manufactures.

Comparisons between counties are difficult because of the many changes to county boundaries in the first four decades of statehood, but Illinois’ most populous county in 1820 was Madison, coming in at 13,550. That number would rank as the 21st-smallest of today’s 102 counties. The least populous was Alexander, with just 625 residents. Agriculture was the dominant occupation in each of the state’s 19 counties, with three counties not registering a single person engaged in any other form of employment. The only non-agricultural workers found in Wayne County were the three persons engaged in commerce, in Jefferson County it was the five who worked in manufacturing.

The census found at least one enslaved person in 16 of the 19 counties.

The 1820 Census was the first one in which Illinois participated as a state. It was also the last one in which Illinois stood as the least populous state. By the time the next census was taken, in 1830, the state’s population had nearly tripled, reaching 157,445. Among these new Illinoisans was a family which crossed the Wabash from Indiana that very year: it is at least possible that the 1830 census was the first to count Abraham Lincoln and his family as Illinoisans, though their 1830 arrival in Illinois came very late in the year. In 1830 the number of people held as slaves in Illinois had declined to 747. By 1840 it had fallen to 331 and the 1850 Census did not locate any enslaved persons in Illinois.

By the second census after statehood, Illinois had surpassed Rhode Island, Delaware, Mississippi and Missouri, and ranked 20th in the nation in population, just behind Louisiana. Illinois was on its way up. The 1850 Census found only 11 states still ahead of Illinois in population. The coming years would see an explosion in population in Illinois, helped along by the arrival of the railroads and the thousands of settlers they brought into the state during the post-Civil War economic boom. By the end of the 19th Century, Illinois was behind only New York and Pennsylvania as the third-largest state by population in the United States. In recent decades, Illinois has been slipping in comparative population, now standing as the sixth most populous state in the nation, behind California, Texas, Florida, New York and Pennsylvania.

The 21st decennial census of the state of Illinois will be conducted on April 1, though much activity is already underway. State officials and community leaders have sought to inform the public of the importance of a full and accurate count of the state. To ensure that the entire population of the state is fully counted, the state has established a 2020 Census Complete Count Committee. For more information, visit