Genealogists can not learn enough about ancestral locations. Determine the formation of the county where your ancestor lived. There may have been several boundary changes from the creation of the county until the present day. Look at the county in historical records, in particular census. Where are most of the head of households born? Is there a large group of people in the county from one particular state? Research should be by group, such as family, friends, religious, cultural and social. Consulting a county history would be helpful in learning if there were group migrations into the area.
There are county histories online as well as available on interlibrary loan. For interlibrary loan go to WorldCat at WorldCat. Actual books on Internet can be found at:
Google Books http://books.google.com/
Internet Archive Internet Archive
Family History Archives Family History Archive
Studying migrations to America as well as across the United States can be extremely beneficial in your research. These are very helpful web sites:
Migration Links http://www.migrations.org/links.html
Roots and Routes http://www.rootsandroutes.net/body.htm
Migration Charts International Research - Migration Charts
Historic American Roads Migration Routes http://tinyurl.com/4d222z
Generational intervals average 25 to 28 years, but more recent studies estimate they can be 29 to 34 years. When you have a child's date of birth, even if just a year, and nothing for parents, begin estimating the parents at 25 to 28 years earlier and work from there. You can easily use these generational intervals to create probable date ranges. Write them out so you can see them for your research.
Spouses involved in a first marriage are usually born within a ten year range of each other. Males involved in second marriages will quite often marry a much younger woman, continuing to have children. Women usually bear children between the ages of 16 and 40. However, it is not impossible for women to have children into their late 40s. Normally siblings will be born within a 24 year time frame.
Births were normally two years apart. There quite often will be a gap of years between the birth of the last child and the previous child. The first birth was normally about 1 1/2 to 2 years after the marriage. Gaps between the ages of children can signal miscarriages, still born children, infant deaths, the father being in the military or migrations which separated the spouses.
The legal age for marriage varies, particularly in various cultural and economic areas of the United States. Normally the earliest is 21 for the groom and 18 for the bride.
Research is not complete unless you take the time to study and learn about your ancestors. Contemplate if what you know makes sense. As part of the evaluation process, you should always study the area and the feasibility of the dates.