The 1820 census included six new states: Louisiana, Indiana, Mississippi, Illinois, Alabama and Maine.

For example, the count of free white males between 16 and 18 was a special count, because these individuals were also supposed to be tabulated in the column for free white males of age 16 and under 26.

Census takers were also instructed to count each individual in only one of the occupational columns.

Before 1830, enumerators lacked pre-printed forms, and drew up their own, sometimes resulting in pages without headings, line tallies, or column totals.

This is not to suggest that they are less reliable than subsequent censuses, but that they may require more work on the part of the researcher.