Here is an excerpt from the book "Get Your Greeting Cards into Stores."
Greeting Card Sales Reps work by geographic territories and it is the responsibility of the artist to make sure no territory overlaps with another rep. For example, if you have a rep that covers northern New Hampshire, and another one that covers southern New Hampshire, make sure that the line is clearly divided between them.
A simple way to keep track of territories is to purchase a United States Zip Code atlas:
You can photocopy individual maps and request that the rep outline the area they cover.
States with small populations like New Mexico may be covered by one rep, and the boundaries are clear, whereas densely populated metropolitan areas like New York City, Los Angeles and San Francisco may have several reps in a small geographic area. In these cases, unless these reps all work together in a group, it is critical to make sure you have all the territories mapped out.
Territories tend to be separated by population, and not necessarily by state. A northern California rep might cross the Nevada border to sell in Lake Tahoe because the Nevada rep does not travel that far north. A Chicago rep might dip down into Indiana since the metropolitan area spills over the border.
If you already make your own greeting cards, this book explains how to get your cards into stores and sell them sell nationwide. Included are guidelines on: how to price your cards for a profit, how to get professional feedback, where to find a sales representative and and what industry standards you should follow. All the information is also applicable to gift items, such as magnets, journals, calendars, collectibles, etc.