I’m thinking about size and density. Density is how many people live in a place and how closely they are packed together.

Chicago has almost 3,000,000 people. Mongolia has about the same number of people, but Mongolia is 603,899 square miles, while Chicago is only 233 square miles. Chicago is packing a lot of people into a pretty small area. That’s why it needs so many tall buildings.

It is a little more complicated than that. Of course it is. That’s because close to half of Mongolia’s people live in Ulaanbaatar, its capitol city. In Ulaanbaatar, as many as 4,000 people are living in every square kilometer (Rethinking Ulaanbaatar’s Population) while in the rest of Mongolia you find an average of about 2 people per square kilometer. That means that in most of Mongolia you can travel pretty far before you find other people, but Ulaabaatar looks like a city. A city with half the number of people as live in Chicago is still pretty big!

So it would be pretty easy to describe Mongolia as a country that has lots of people living pretty close together in one city but is pretty empty everywhere else. And, it would be true. So how do we describe the United States?

Alaska has about the same population density as Mongolia–less than 2 people per square mile. Wyoming has only 6 people per square mile, and Montana only 7. Quite a few other states (North and South Dakota, Idaho, New Mexico, Nevada…) are also large empty areas.

So here’s the question: What might people in Wyoming have in common with people in the Mongolian countryside? What might people in Ulaanbaatar have in common with those of us in the Chicago area and other big cities?

Who has more in common, people who come from different parts of the same country or people from similar geographical areas?

Here’s a mystery: Are these two pictures from the same country? If you click on the pictures, you’ll find out, but that’s no fun! Think first about what information you would need to figure it out yourself. You can leave a comment with your ideas.