For the entire country?  For free?  :-) 

It's a generous offer, but I needed a quick and free solution.  I've been finding that realvantagepoint.com (run by Black Knight fka servicelink I believe) has been the best answer.  It doesn't MAP, but it IS linked in to every state and by putting in an address, it brings up county name AND parcel ID AND at least part of the legal description.

But Allen, if you could set up something yourself, you could probably market it to the abstractors.  Not just for county line problems but mapping issues when we're trying to figure out screwy legal descriptions.  (Mapping by hand works, but would love to use what my own county's mapping department uses!  Just can't afford the hundreds [or thousands] of dollars they pay for that GIS system.)