The first mistake people make with regard to census data is to presume or assume that it is correct. Like other primary source documents, census records are filled with errors. The two main causes of error come from, first, the supplier of the information to the census taker; and, second, the enumerator himself. Because the census record does not supply the name of the person who talked to the census taker, one cannot verify the veracity of the info. Perhaps the family wasn't home that day and a neighbor supplied the information. Perhaps Aunt Tilley, the family know-it-all was visiting and took it upon herself to answer the questions. She may have assumed that her niece-in-law was born in Alabama because she knew that was where the couple married. The fact that the woman in question was born in Kentucky and the family had moved to Alabama when she was very young may not have ever come up in conversation.
When it comes to state of birth, there is another possible cause of error that people often overlook, especially in older census records. The approximate year of birth needs to be compared to the date a particular state came into existence. The most common error centers around just prior to the time of the Civil War. If your ancestor was born in Virginia, it is possible they were born in the area that is now West Virginia. You will need to search for records in both states. This is also a problem when researching states and having oral family tradition come into play. Does family lore say an ancestor was born in Arkansas? Arkansas Territory was created out of the Missouri Territory and included most of what is now Oklahoma -- except the Oklahoma Panhandle. Eventually, the Arkansas territory was reduced in size twice before it finally became settled into the present boundaries. That was in 1824.
Are there family stories of Indian Territory? To most of us nowadays, that means Oklahoma; but years ago that meant most of what is now known as Indiana, but was then also called Indiana Territory. What pops into mind when you think of the Northwest Territory? No, it's not Washington, Oregon, Idaho and Montana. In 1787 the government created the Northwest Territory and it included areas previously been known as Ohio Country and Illinois Country. Although Ohio became a state in 1803, it wasn't until 1836 that Ohio and Michigan actually settled boundaries between the two areas. Yes, family historians need to study history.
When it comes to state of birth, there is another possible cause of error that people often overlook, especially in older census records. The approximate year of birth needs to be compared to the date a particular state came into existence. The most common error centers around just prior to the time of the Civil War. If your ancestor was born in Virginia, it is possible they were born in the area that is now West Virginia. You will need to search for records in both states. This is also a problem when researching states and having oral family tradition come into play. Does family lore say an ancestor was born in Arkansas? Arkansas Territory was created out of the Missouri Territory and included most of what is now Oklahoma --- except the Oklahoma Panhandle. Eventually, the Arkansas territory was reduced in size twice before it finally became settled into the present boundaries. That was in 1824. Are there family stories of Indian Territory? To most of us nowadays, that means Oklahoma; but years ago Indian Territory included what is now Indiana, Illinois and Ohio.
All this leads to the second rule of genealogy -- the preponderance of evidence. I have addressed preponderance of evidence in prior articles, but it cannot be overemphasized. If a census form, a birth certificate, a death certificate, a bible record, etc. all say your ancestor was born in New York you can be 99.9 percent sure that is where the person was born. If three of four references say New York and one says Pennsylvania, then you can be 75 percent sure that New York is the place. If you have an equal number of sources pointing to different states -- more research is needed.