Real-estate Parcel Data - Where can I find datasets?

I am interested on how Zillow.com is able to get the boundaries of a home/lot. I would like to know if this data is open-data and if so, if there w开发者_开发技巧as a way I can hook into it?

Any and all advice will be greatly appreciated!

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Parcel Data are generally maintained by the County Assessor's office. There are over 3000 counties in the US each with different data quality, policies, etc. Many counties provide the data free via their websites, others charge a small fee to cover their cost of providing the data, others still don't have it in digital form.

For example parcel data for Seattle, WA can be downloaded from the King County Assessor's website, http://www.kingcounty.gov/operations/GIS/GISData.aspx

If you need data for the whole country you'll probably want to go with a commercial provider. Some providers offer free access for non-commercial use. For example, http://developer.urbanmapping.com/catalog/dataset/umi.us_parcel, has parcel data for about 1,300 counties which can be used via their Mapfluence API