Using United States Postal Service Mail Carrier Routes is an effective way to create a mailing list. 

Mail Carrier Routes define the daily route of a postman and average 300 to 500 deliveries. 

Including an entire route in a mailing qualifies it for saturation postal rates - the lowest available.

Compared to a zip code mailing (which can have 10,000 deliveries or more) picking individual carrier routes allows you to target specific neighborhoods. 

In addition to precise geographic targeting, the average age and income of the residents of the carrier route are also available.

The illustration below shows a typical zip code with mail carrier route boundaries. The business shown in the center of the map can pick specific neighborhoods using carrier routes. The carrier routes chosen do not have to be adjacent to one another and can even include those from another zip code.