ECONOMIC GEOGRAPHY • E-FREE TRANSLATION.COM • Definition of Economic geography

... to a great degree the complementary relation of highlands and lowlands. The plains possess what the mountains lack. This is a fundamental fact of economic geography, and inevitably leads to historical results. The marauding expeditions of mountain peoples first acquire historical importance, either when the raids after long continuance end in the conquest of the lowlands, and thus augment the resources and population of the highland state; ...

— Influences of Geographic Environment - On the Basis of Ratzel's System of Anthropo-Geography • Ellen Churchill Semple