Ida County IAGenWeb

The 1905 Iowa census was written on 3 X 5 inch cards with a card for each person.   A card number (in the upper left corner) was assigned to each card. When a census taker came to a family, the father would be given the first card number (for example card # 100).  The wife and children would follow in numerical order; for example, the wife would be card number 101, and the children, card numbers 102, 103, 104, etc.  The cards were then filed in alphabetical order by their names (which means looking at the card of any person will not tell you who the parents, children, or siblings were).
There was also a directory created in 1905 listing the card numbers in numerical order by county and township or town which included each person’s  name, post office address, and card number.  Using this directory, you can tell the members within a particular family.  This directory lists the names of the family members together, in numerical order (again, father first, then mother, then children).  The 1905 Directory is available on Ancestry.com (for a fee), while the original census cards are available on Family Search.org.   The original census cards included such information as: card #, name, address, sex, color, age, place of birth, parent’s birth place, number of years in the U.S., number of years in Iowa, occupation, and military service.