Questions on the census change from decade to decade, of course, as society changes. Here are some noteworthy "debuts" in the following years, according to Connie Potter, head research archivist at the National Archives in Washington:

1880: First time the form asked for addresses. It also was the "only time they asked if the person was sick or disabled on the day of the census, so you can find people with rheumatism or epilepsy," Potter said.

1900: First to ask how many children a woman had borne, and how many survive. "That was not always answered," Potter noted.

1910: First to ask if the person was out of work on April 15 of that year and the number of weeks he or she had been out of work in 1909. Also asked if you were a survivor of the Union or Confederate army.

1920: First to ask if you were a naturalized citizen, and if so, when that had occurred.

1930: First census to ask how much people paid for a home, or how much they paid in rent. "That allows us to find out what property was worth," Potter noted.