Natalie is a teacher and holds an MA in English Education and is in progress on her PhD in psychology.

How are cities organized? This is a central question that has been explored for almost a century. In this lesson, we'll look at three of the common models to explain urban structures in America: the Burgess model, the sector model, and the multiple nuclei model.Urban AreasSally is very interested in her city. She likes to walk around a lot and has noticed that there are distinct neighborhoods that seem to serve different purposes. There are areas with a lot of skyscrapers and businesses, and areas with factories and low-rise buildings. There are areas where people live in apartment buildings, and areas where people live in houses. Every area of her city seems different to Sally!

An urban area is a place with a high population density and mostly non-agricultural jobs. That is, there are a lot of people and not very many of them work in farming and ranching. Like most other cities, Sally's city is an urban area.

How are urban areas arranged? Sally has noticed different neighborhoods, but she wonders how the neighborhoods are laid out on a map. To understand the way that urban areas, like Sally's city, are arranged, let's look at three popular models of urban structures: the concentric zone model, the sector model, and the multiple nuclei model.

Concentric Zone ModelSally has noticed that there are a lot of different types of neighborhoods in her city and is wondering how those neighborhoods might appear if they were mapped out.

The simplest and one of the earliest models of urban arrangement is the concentric zone model, which is sometimes called the Burgess model after Ernest Burgess, who first wrote about it in 1923. The concentric zone model says that a city is made up of neighborhoods shaped like rings that circle around a central business district. When mapped out, the concentric zone model kind of looks like a bull's eye.

Burgess identified five concentric circles, or zones, that he believed were common in cities. They are:

Zone 1 is the central business district or downtown area of a city. This is the center of the city, where there are often skyscrapers and lots of businesses.Just outside of zone 1 is zone 2, which is made up of many factories. This area is where many goods are manufactured. Like the downtown area of zone 1, zone 2 does not have a lot of homes. Instead, these two zones are where most people work.Circling the factories in zone 2 is zone 3, which is a working class neighborhood. This is where many of the factory workers live, mostly in apartments.Zone 4, which surrounds zone 3, is a middle class neighborhood. Here, the people live in modest houses instead of apartments.Finally, zone 5 is the outermost ring in the concentric zone model. It is an upper class neighborhood, made up of expensive houses where the richest citizens of the city live.The concentric zone model, as we mentioned, is one of the first models to try to explain urban structures. And it kind of makes sense to Sally. After all, she's noticed that there are factories near the downtown area in her town, which echoes the ideas of zones 1 and 2.

Sector ModelBut there are some things that don't make sense to Sally. When she looks at the bull's eye map of the concentric zone model, it looks very neat. But the neighborhoods in her city just don't seem to be that organized and neat.

In 1939, Homer Hoyt expanded on the concentric zone model to create the sector model, which is also called the Hoyt model after him. The sector model proposes that zones in a city extend outward by transportation, such as railroads and highways.

Because the neighborhoods in the sector model lie along major transportation, a neighborhood could radiate outward from the city center to the farthest areas of the city. If the concentric zone model looks like a bull's eye, the zones radiating outward in the sector model make it look like a pie.

According to Hoyt's model, a slice of the city pie could have the same general demographic from the downtown area to the outermost parts of a city. That is, one slice could be made up of mostly middle class residents and, instead of being an orderly ring like in the concentric zone model, the slice would push outward from the downtown area. The sector model fits British cities better than it does American cities, but it still has some similarities to urban areas in the U.S.

Sally can see how the sector model might fit her city. After all, it's not as neat and organized as the concentric zone model and she's noticed that there are some neighborhoods that seem to stretch across the city instead