Genealogists sometimes forget that political subdivisions are largely arbitrary or follow only major geographic features like rivers and mountain ranges. But have you noticed how many straight lines there are on maps? Last time I checked, there were no straight lines in nature. (I know, this is particularly true, but generally speaking, the boundaries between U.S. states are straighter than any naturally occurring physical phenomena).
A common example, is that of two towns located closely to each other on a map, but in reality separated by a high range of mountain. Looking at a map without topographical features, will obscure physical realities which may limit travel between apparently proximate communities.
But there is a more subtle factor that influences genealogical research in a dramatic way but is seldom recognized by researchers. That is the effect of the lack of modern transportation modes on family relationships in the not-too-distant past. For example, I can get in my car and drive to Apache County, Arizona in about 3 1/2 hours. A hundred years ago, the trip would've taken the better part of a week on a fast horse. Only fifty years before that, such a trip would've taken a week in a fast buggy or two weeks depending on whether or not the group traveling had adequate transportation. So, the real distance between two points on a map is not measured in miles or kilometers but in the time it takes to travel the distance between the two points.
Ignoring these historical facts, brings about a misunderstanding of the relationships between the various parts of any family organization. Another example, if a family left Germany in the 1850s to move to the United States, it was entirely possible that they would never see any of their relatives left in Europe during their lifetimes. Even on a smaller scale, inside the United States, a movement across state or even further across the country, could isolate members of families from each other permanently. It is nearly impossible to imagine this kind of condition existing today when I have members of my own family commuting across the United States every week. My brother-in-law, just contacted us that he was driving a truck from California to Texas and would pass through Phoenix. This kind of mobility was entirely impossible just a few years ago.
An obvious result of this historical fact is that movements by families was not taken lightly or on a whim. There was always a reason, for any movement. In addition, most familial movements were undertaken following established settlement routes or in response to economic or social conditions. Unlike today, young people when leaving their family, usually did not have a job offer halfway across the country. The most common circumstances were when rural workers migrated to the cities looking for better working conditions.
In doing genealogical research, it is absolutely necessary to broaden your search for family members throughout any particular geographical area. For example, in U.S. census records always look for family members on adjacent census sheets. Census enumerations were done in a systematic way geographically and it was not uncommon for family members to be physically located close to each other. The same principle, can be extended to practically any research in any type of documents. Another example, collections of World War II and World War I draft registration cards should be searched to see if other family members registered at or near the same time. In smaller towns, it is always a good idea to search the entire census record for the locality for each year in which the census was taken. Many smaller enumeration districts had less than 20 total census sheets.
Failure to take into account the time it took for people to travel between two areas is often at fault for making unsupported claims to relationship. If you found a family name of an ancestor in Rhode Island, it would be illogical to assume that a family with the same name living in Georgia was related without some very specific evidence to support such a conclusion. But I have seen just such conclusions made on virtually no evidence. On the other hand, many genealogical researchers seem to feel that their families lived in a vacuum because they seldom search for related families in each of the geographical places where the family lived.
Both maps and timelines are valuable helps in resolving realistic distance issues. If someone lived in county in Virginia shortly before they got married, it is unlikely that the marriage took place in Maine or Vermont. Not impossible, just highly unlikely. In looking for your ancestors, the absolute first step is to try to put them on a map. That is, look for any and all know places on maps to see how they are related and whether or not the places fit logically into the physical reality of the areas in question. At every step in your research never leave the map for very long. Keep the geographical perspective.