title: Retrieving population density data
body: <p>I need to figure out whether not a given location is considered urban or rural. I take it that the best way to do this is by looking at the population density of the city/state or province/country combination.</p>
  
  <p>The kicker is that we're using this for data mining. Generally, mapping APIs that could do this have a requirement that each request must be in response to a single user action. This doesn't fit that criteria...using a web service, we would be making hundreds of web service calls for any single user action. So I think we can't really use something like the Google Maps API.</p>
  
  <p>The problem is, what is available? Are there any databases ready to download which I can use to retrieve this data, or web services that actually allow data mining? I am using PHP, though the programming language doesn't really matter. I'm sure if I can get the data, I can get it to work with PHP.</p>