A lot of Google Maps use cases require to plot regions, such as sales sectors, maintenance zones or potential customer markets.
Doing this manually is often tedious and error-prone. Since a lot of use cases are based on administrative boundaries (states, cities and others), our best option is to use the administrative boundary as a starting point.
For example we have a customer whose sales representatives are deployed on specific zones. Each zone is typically based on a French "département" (an administrative region). It can be a full département, or half a département, or a third...
For a bit of fun I wrote a quick demo of this approach. The demo application allows you to split a département in two zones. Each zone will be affected to a sales representative.
You can then use Google Maps' geocoding feature to test any address you want and see if it lands on one of the zones you just created.
The Github code is available here : https://github.com/dhatanian/gmaps-zone-creator
The demo application is available here : https://gmaps-zone-creator.appspot.com