Week 3: Americans on the move.....

http://www.nytimes.com/interactive/2009/03/10/us/20090310-immigration-explorer.html

This is an interactive map which shows the patterns/distributions of the American population.
What patterns of change can you identify?
Why do people move and migrate? Why are Americans so mobile?
Are they same reasons for each period of history?
Are the patterns the same for each ethnic group?
Is there evidence that environmental factors" are influential? - eg the Population patterns of the Great Plains?
Plenty of questions but, remember, the simple approach - Where? And, why there?
Good wishes,
John