The concept of 'Compage' was introduced by American geographer Derwent Whittlesey in 1954 as a way to define and understand regions based on their functional integration rather than mere spatial contiguity or homogeneity. It represents a sophisticated approach to regionalization, emphasizing the dynamic interrelationships between various elements within a geographical area.

At its core, a compage is a functionally organized region where a specific set of physical, biological, and cultural features are not just present together, but are intricately interrelated and interdependent, forming a coherent and functioning whole. Unlike formal regions defined by shared characteristics (e.g., a climate zone), a compage is defined by the functional connections, flows, and interactions that bind its components together. These interactions can be economic, social, ecological, or political.

Key aspects of the compage concept include:

1. Functional Interdependence: The defining characteristic is the mutual dependence and interaction among the region's components. Changes in one element are likely to affect others, highlighting the systemic nature of the region.
2. Holistic View: It encourages a holistic understanding, considering how different aspects of the natural environment (e.g., climate, hydrology, landforms) and human activities (e.g., agriculture, industry, settlement patterns, cultural practices) interact to create a unique regional system.
3. Dynamic System: A compage is not static; it is a dynamic system that evolves over time. The functional relationships and the components themselves are subject to change, leading to shifts in the region's character.
4. Hierarchical Structure: Compages can exist at various scales, from local to global, with smaller, more specialized compages potentially nested within larger, more generalized ones.

For example, a river basin can be considered a compage. The river itself, its tributaries, the surrounding land use (agriculture, forests, urban areas), human settlements, and economic activities are all functionally linked. The health of the river affects the productivity of agriculture and the well-being of the population, while human activities in turn impact the river's quality and flow. This intricate web of relationships defines the river basin as a functional compage.

Whittlesey's concept of compage moved beyond purely descriptive regional geography towards a more analytical and process-oriented understanding of regions, emphasizing the underlying functional organization and interconnections that give a place its distinctive character.