Census information is necessary to see where your family lived at a point in time and who lived in the household at the same time. It is important to look at families in the same area because often relatives lived near each other.
The US was the first country in the world to make a census a mandatory part of its constitution. Article 1, Section 2 of our Constitution mandates that a census must be done every ten years.
Free databases to locate census information include those listed below: