Geo Database
September 2, 2011 3:21 PM   Subscribe

Where I can find free United States geographic databases? I need a database with relationships between all zipcodes, areacode,cities,states,counties,neighborhoods, all with coordinates and detailed information if possible. How up to date does not matter, and I am looking for something free.
posted by digdan to Computers & Internet (6 answers total) 10 users marked this as a favorite
 
Are you looking for national-scale coverage, or data for specific states?

Off the top of my head, The NRCS data gateway has GIS data available by state and county, geodata.gov has a bunch of stuff, and Census TIGER data is the primary source for demographic data like census blocks, block groups, tracts, cities, etc.

All of this data is in GIS format - typically Esri shapefile. The spatial data is there, but coordinates aren't typically shown in the tables - you'd need GIS software to extract the coordinates.
posted by indeterminacy at 3:40 PM on September 2, 2011 [1 favorite]


Not an answer to your question, per se, but just a warning: zipcodes don't necessarily map cleanly to contiguous geographical areas. They're actually just collections of postal delivery routes, so different sides of a street may be in different zipcodes, or a zipcode may skip a portion of a street. Many cross county or city boundaries, and some cross state ones. Some providers providers may claim to give you zipcode-to-polygon mappings, but be skeptical of them. I would guess that area codes are similar.

Because of this and various other issues (not all states have counties, and those that do treat them differently: in Virginia, counties and cities are mutually exclusive, for example) make cobbling this kind of dataset pretty hard, so the free sources of it tend to be of pretty crap quality, particularly for the stuff that changes a lot. The commercial stuff is much better.

If you do want to go free, though, the Census has a bunch of stuff on at least some of those. You may also be able to get information about neighborhoods from Open Street Maps, as I know there are at least some fledgling efforts there in that area.
posted by andrewpendleton at 3:49 PM on September 2, 2011


Popped in here to say essentially what indeterminacy did, but to reiterate andrewpendleton's warning: Yes. My town has two zip codes, my side of town is 94952. This is also shared with the Coast Guard base several miles west of town, so if you do geographic searches based on that zip code you'll get places nowhere near town, and if you search for the closest post office to that zip on the USPS.gov site, the town's post office doesn't actually show up until the second page of results.
posted by straw at 4:19 PM on September 2, 2011


Zillow has downloadable neighborhood boundaries.
posted by djb at 5:45 PM on September 2, 2011


It's probably not everything you want, but you might find some useful things at Melissa Data.
posted by thirteenkiller at 6:33 PM on September 2, 2011


This is the Holy Grail of GIS, so if you find the One True (Free) Database, please let the rest of us know.
posted by desjardins at 11:50 AM on September 13, 2011 [1 favorite]


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