Reporting areas, or forecast cities, are the means in which observations and forecast information is disseminated on AirNow.gov, and are required before a forecast can be issued. You can have multiple reporting areas for each agency, and multiple verification sites for each reporting area. For example, the state of Louisiana has 8 reporting areas. Some of these reporting areas only have 1 verification site, while others (like Baton Rouge) have 5 or more. The highest AQI readings from the sites in a reporting area will appear on the AirNow.gov Current Conditions page.
It is suggested that sites in close proximity to one another be included in the same reporting area. Sites that are isolated usually will require their own reporting area, if any. Agencies can add/remove reporting areas by emailing email@example.com with their request.
To add or remove verification sites to an existing reporting area, see this forum post