Central place theory why settlements space out the way they do.
Central place theory is Christaller’s model of why cities and towns vary in size and spacing, built on the ideas of threshold and range. Here is the AP Human Geography definition, the terms you must know, and how it shows up on the exam.
The one-line definition
Central place theory is the geographer Walter Christaller’s 1933 model explaining the size, number, and spacing of settlements. It says cities and towns exist to provide goods and services to the surrounding area, and a predictable hierarchy of larger and smaller places emerges from that role.
The central place theory AP Human Geography definition that earns points is short: settlements are spaced to serve a surrounding market area, with bigger places offering rarer, higher-order services.
The terms you must know
Two ideas drive the whole model.
Why it matters in AP HuG
Central place theory anchors the cities and urban land use unit, and the threshold-and-range pair shows up constantly. A high-order service like a specialist hospital has a high threshold and range, so it sits in a few big cities; a convenience store has a low threshold and range, so it appears in nearly every town. Expect questions that give you a service and ask where it would locate.
Common mix-ups
Do not confuse threshold with range. Threshold is about how many customers you need to survive; range is about how far they will travel to reach you. High-order goods have both a high threshold and a high range, which is why they cluster in large cities rather than small towns.
Frequently asked questions
Quick answers — written by humans, not a chatbot.
What is central place theory in simple terms?
It explains why settlements vary in size and spacing: each serves a surrounding market area, and larger places offer rarer, higher-order services that need more customers.
What is the difference between threshold and range?
Threshold is the minimum number of customers a service needs to survive. Range is the maximum distance people will travel to use it.
Who created central place theory?
The German geographer Walter Christaller proposed it in 1933 to model the distribution of settlements.