The big flat areas have low population density BECAUSE of all economy of scale farming. Look at California: You've got 4 metropolitan areas, 2 of which (the Bay

The big flat areas have low population density BECAUSE of all economy of scale farming. Look at California: You've got 4 metropolitan areas, 2 of which (the Bay Area and Los Angeles) are in coastal areas that have geographically convenient access to the big flat area with farms, one (San Diego) in a big flat desert, and one on the river in the big flat area (Sacramento). Chicago's surrounding areas are flat farmland. Portland and Seattle likewise have river access to their state's big flat areas. What's between the Rockies and Appalachia? Big flat farms.