Ancestry.com has maps showing where Caldwells lived in the United States in 1840, 1880, and 1920, as well as in England and Wales in 1891.

See, e.g., http://www.ancestry.com/learn/facts/Fact.aspx?fid=6&ln=Caldwell

Surprisingly the Caldwells in England and Wales were most heavily concentrated in northwestern England, just above Wales. Is this Cumbria? The fewest Caldwell families were in the midlands. In several midland counties there were no Caldwells.

In the United States of 1840 the greatest concentration of Caldwells was in the Appalachians. By 1920, the greatest concentration was in California, Texas, North Carolina, and Ohio.