ZIP codes are used by the US Postal Service to identify an area where mail is delivered. The use of the ZIP code in small area analyses is widespread despite its limitations. The limitations include foremost the non-homogeneity of the ZIP code unit with respect to geographical size and with respect to population size. For instance, California wide in the year 2000, the number of births in ZIP codes ranged from 0 to 2745 with a mean of 246 births and a standard deviation of 368 births.

The obvious advantage of using the ZIP code as the unit of analysis is its wide availability: ZIP code information can be easily collected compared to information on census block group. The wide availability of ZIP code level data allows the combining of ZIP code level information from different databases.

The table below lists all ZIP codes for Sonoma County that were included in the most recent list of available ZIP codes. The listing as well as the map coordinate files for the maps included in this report were based on data products that were obtained from the TeleAtlas company.

Among the USPS ZIP codes, not all have a physical service area. Point ZIP codes pertaining to a unique ZIP code (ZIP codes pertaining to a single site, building, organization) or P.O. Box cannot be associated with a physical area on a map. For the purposes of this report any counts in point ZIP are included in the counts for the enclosing ZIP. For each point ZIP, the enclosing ZIP is listed in the table below.

ZIP Inventory Table

ZIP Code Inventory for Sonoma County, 2007

ZIP Code	Post Office Name	Zip Code Type	Enclosing ZIP Code
94515	Calistoga	Non-unique ZIP
94558	Napa	Non-unique ZIP
94574	Saint Helena	Non-unique ZIP
94922	Bodega	Non-unique ZIP
94923	Bodega Bay	Non-unique ZIP
94926	Cotati	Unique ZIP	94928
94927	Rohnert Park	P.O. Box	94928
94928	Rohnert Park	Non-unique ZIP
94931	Cotati	Non-unique ZIP
94951	Penngrove	Non-unique ZIP
94952	Petaluma	Non-unique ZIP
94953	Petaluma	P.O. Box	94952
94954	Petaluma	Non-unique ZIP
94955	Petaluma	P.O. Box	94952
94972	Valley Ford	Non-unique ZIP
94975	Petaluma	P.O. Box	94952
94999	Petaluma	Non-unique ZIP	94954
95401	Santa Rosa	Non-unique ZIP
95402	Santa Rosa	P.O. Box	95404
95403	Santa Rosa	Non-unique ZIP
95404	Santa Rosa	Non-unique ZIP
95405	Santa Rosa	Non-unique ZIP
95406	Santa Rosa	P.O. Box	95401
95407	Santa Rosa	Non-unique ZIP
95409	Santa Rosa	Non-unique ZIP
95412	Annapolis	Non-unique ZIP
95416	Boyes Hot Springs	P.O. Box	95476
95419	Camp Meeker	P.O. Box	95472
95421	Cazadero	Non-unique ZIP
95425	Cloverdale	Non-unique ZIP
95430	Duncans Mills	P.O. Box	95472
95431	Eldridge	P.O. Box	95442
95433	El Verano	P.O. Box	95476
95436	Forestville	Non-unique ZIP
95439	Fulton	Non-unique ZIP
95441	Geyserville	Non-unique ZIP
95442	Glen Ellen	Non-unique ZIP
95444	Graton	Non-unique ZIP
95446	Guerneville	Non-unique ZIP
95448	Healdsburg	Non-unique ZIP
95450	Jenner	Non-unique ZIP
95452	Kenwood	Non-unique ZIP
95461	Middletown	Non-unique ZIP
95462	Monte Rio	Non-unique ZIP
95465	Occidental	Non-unique ZIP
95471	Rio Nido	P.O. Box	95446
95472	Sebastopol	Non-unique ZIP
95473	Sebastopol	P.O. Box	95472
95476	Sonoma	Non-unique ZIP
95480	Stewarts Point	Non-unique ZIP
95486	Villa Grande	P.O. Box	95421
95487	Vineburg	P.O. Box	95476
95492	Windsor	Non-unique ZIP
95497	The Sea Ranch	P.O. Box

Source: TeleAtlas

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