Every name in a US census record was written by hand by a single person — a person who walked to your ancestor’s door, asked a few questions, wrote down what they thought they heard, and moved on to the next house.

You are tracing a family line and you can account for most of the children — but one of them, always the youngest or one of the youngest, simply does not appear in the census. No record. No mention. Just a gap where a child should be.

You have traced your family back to an immigrant ancestor — perhaps Irish, Italian, Polish, or German — and you know they were alive and living in the United States during a particular census year. So why can’t you find them? The answer is almost always timing.

Picture this: it is a Tuesday morning in June 1900. A man with a notebook walks up to a tenement building on the lower east side of New York. He knocks on the door of apartment four. A woman opens it. She speaks almost no English. He speaks no Polish.

You find your great-great-grandmother in the 1880 census aged 34. In 1900 she’s listed as 48. In 1910 she’s 55. The maths doesn’t add up — and you’re not going mad.

You find your great-great-grandmother in the 1880 census aged 34. In 1900 she’s listed as 48. In 1910 she’s 55. The maths doesn’t add up — and you’re not going mad.