Example - get cities in the US:

GET /backstage/api/1.0/resources/countries/US/cities

{
   "results": [
      {
         "name": "AL",
         "value": "Alabama"
      },
      {
         "name": "AK",
         "value": "Alaska"
      },
      {
         "name": "AR",
         "value": "Arkansas"
      },
      {
         "name": "AZ",
         "value": "Arizona"
      },
      {
         "name": "CA",
         "value": "California"
      }
      // Additional rows (objects) omitted
   ]
}

📘
You must provide a valid country code - see: Get list of Countries.
The country code is not case sensitive.
If you provide an invalid country code, the API returns a JSON object with 404 Not Found.