The 1850 census saw a dramatic shift in the way information about residents was collected. For the first time, free persons were listed individually instead of <answer>by head of household</answer>. There were two questionnaires: one for free inhabitants and one for slaves. The question on the free inhabitants schedule about color was a column that was to be left blank if a person was white, marked "B" if a person was black, and marked "M" if a person was mulatto. Slaves were listed by owner, and classified by gender and age, not individually, and the question about color was a column that was to be marked with a "B" if the slave was black and an "M" if mulatto.
How were free persons listed in the US census prior to 1850?
by head of household