Routes taken were well known to the pioneers. They knew of the canals, river crossings, trails, wagon roads, and paths they had to use in order to arrive at their new destinations. Routes were seen not only as routes to other locations, but they were also aware of how such well-traveled routes provided a boost to trade for those along the way.
A good example of this was my fourth great-grandfather Adam Smith Jr., who started a tavern along side the National Road and provided rock for the builders of the road in the 1830's. The National Road was originally called the Cumberland Road because it started in Cumberland, Maryland. It traveled through central Ohio west to Indiana and Illinois and is today US 40. It was started in 1811, which was the same year Adam Smith Jr. moved from Virginia to Ohio. He obviously was well informed of the route and took advantage of its existence.
My second great-grandfather, Joseph Owen traveled through the Cumberland Gap on the "Wilderness Road" in 1845. He moved from Person County, North Carolina to Webster County, Kentucky. His move was well documented. The story of the wagon train added a lot of colorful history to my family's epic.
If you have a family that seemed to have moved to another location in the 1800s, it may assist you to discover what noted road or trail lead out of the area and where the general population were bound. An ancestor of mine ran a pack mule team from Iowa to Sheridan, Wyoming. I discovered that many in the area used this route, and it was Sheridan, Wyoming where I found a branch of my family had moved. Another tool can be the migration project, often run by county genealogical society web sites. They invite new entries of who moved from where to their county and when this move occurred. A quick glance over such a list will soon illustrate the most popular routes that people in the area used.
Another tip is that it was common for pioneers to follow along at pretty much the same latitude. They were accustomed to a certain range of weather and the crops that grew at that latitude, and often did not part dramatically from it. Thus, families would not move from the north to the south as much as from east to west. A study of the local papers of the time may also give the researcher insight into what distant locations were popular and being talked about. Jobs, the opening up of new territories or the establishing of new rail lines often prompted individuals to migrate. Know your history such as, when were the gold rushes, etc. and perhaps you can figure out where a relative disappeared to. New land opening up was often the cause of such migrations, so check when the latest land rushes occurred.
For sure there were many shorter and less acclaimed moves by families from the east to the west. There are 18 of the most well known trails listed on web site: Early American Trails and Roads.
We should not forget the waterways and canals which were also used. These routes were unique in themselves and have there own jargon. A thesaurus of terms for waterways can be found on pages 3-5 of the following web site: http:///freepages.genealogy.rootsweb.com/`gentutor/rivers.html. There are also links to information concerning flatboats, keel boats and steamboats in the 1800s, as well as canals, rivers, and lakes.
An ancestor or ancestral family moving to a new location is always a momentous and key incident in one's family history. I hope this helps in finding out more about their journeys.