I read an article called Moving On by Barbara Kransner-Khaitin in a 2001 issue of Family Tree Magazine that was really good. In the article, she covered the reasons and migration patterns of our ancestors and states that by studying these patterns, they might provide insight into who are ancestors were.
People and families often moved in large groups for a variety of reasons. Several migrations or “fevers” as they were known were:
Genesee Fever: in the 1790′s the New Englanders moved into the Genesee Vally region of western New York.
Ohio Fever: Harsh weather forced many New Englanders to move into the fertile farmlands of Ohio after the economic fallout from the War of 1812.
Michigan Fever: Over 200,000 people from New England, western New York, Virginia and North Carolina migrated to Michigan between 1830 and 1840.
Oregon Fever: More than 350,000 made the 2,000 mile westward trek to new destinations in the west.
Gold Fever: Around the 1850′s, many pushed westward because of financial hardships and hopes of finding gold easily. Little did they know that it would be very difficult and more often than not, would find nothing but more hardships.
As you can see from the above, the reasons for migrating were often economic and weather related.