A common misunderstanding is that people would travel either alone or in single family groups. This is not the case. Unlike today where people travel often on their own to new homes in the early days there was strength in numbers. This becomes a very important issue when using the Census to pinpoint family groups and areas of origin.
When reviewing the US census records it is important to use the up ten and down ten rule. Once the person you are looking for is identified on a particular census sheet it is now time to use the rule. Look at the ten family groups previous on the census and the ten families after you ancestors group. Notice surnames and states of origin that are common. These will be very important clues to doing your search.
During a recent search I was able to use this technique with great success. I was having problems with locating the original state of origin for a family member. They were living in Huron Co., OH from about 1845 to the early 1900's. From information I obtained I new that the family had originated from Ashtabula Co., OH, but the eldest members had been born in Massachusetts. They were in Ashtabula at a very early date between 1820 and 1845. From doing will and land searches in Huron Co I determined that my ancestor has a brother living in the same town. This helped me in locating where they lived in Ashtabula. They had both lived very close to each other through several census records and ended up being buried very close to each other in a cemetery in Huron.
When looking at the Census records for 1820 and 1830 in Ashtabula I was able to identify several heads of household sharing the same name. On the brothers census in 1830 two people living with him were over 70 years in age 1 male and 1 female. Combining this information with tax records and voting records I was able to determine that this was the boys father. With additional search I was able to determine that other people with the common surnames were male siblings. Without using this technique I would not have been able to connect the family back to the 1630's.
So when you are doing your next census search remember families and old neighbors moved in groups. Check the names and locations where they came from. Searching some of the biographies or obits on the neighbors may help in determining your ancestors origins.