The location module for Drupal 6 is a robust module. On most projects, it gives us 100 percent of what we need. Proximity searching based on zip code is built-in and fairly painless to setup. I’ve recently been tasked to also allow proximity searching based on City. As you might imagine, the request is very similar. Both methods require the use of latitude and longitude (decimals). The difference is that instead of querying the database for latitude and longitude based on zip code (it’s usually termed postal code in Views, Location, etc.), we’re asking for the coordinates of a city. You’ll find that many cities have multiple zip codes, each of which is a row in the location module’s zipcodes database table. In this example, I’m not giving a real honest attempt at solving this issue, but rather I just return the first coordinate that matches the city.