All of our boundary data uses SRID 4326 or WGS84.
Using sophisticated algorithms that strictly interpret monthly data feeds from the US Postal Service, our County GIS data is built from the address up to represent on-the-ground reality. Each boundary is closely tied to the street network as defined in the TIGER/Line® street data network.
There are about 3,000 Counties (or county equivalents) in the US. Most of the changes are quite small, others are significant.
Our County Boundaries cover the entire United States.
No. County boundaries are not made with polygons but with collections of deliverable addresses. Boundaries have to be created using those address clusters and given latitude and longitude coordinates. This is an extensive process that falls outside the mission of the USPS. In fact, USPS.com refers all visitors looking for ZIP Code maps to our data.
The enormous effort and amount of resources required to create accurate County Boundaries often entices companies to take short-cuts. The fact is that some are easy to map and others are difficult in that they require thought and research. Many data providers over-generalize boundaries by simply dropping those that are hard to map.
We never takes those short-cuts. Strict data methodologies and quality assurance checks ensure that each boundary accurately capture the true area, not just those that are easy to map.
Counties are not really polygonal. Counties can be non-contiguous pockets of addresses or areas. Additionally, topological features such as water (a bay or river - especially with islands) or mountains can create pockets.