While the tax based mapping system is what you referenced, there's also the ONYX Hunt gps maps.
Note they cost money and make several versions, some which just give you public land. The premium version gives you parcel boundaries and landowner names. They also make versions for handheld GPS and have a phone app.
The GPS version with private landowner names is around $100 I think, per state. Can get at Cabelas and comes on a physical micro SD chip to put in your device. Then you have it forever, but doesn't update, so if properties change hands and so forth it doesn't know, unless you buy a new chip.
The app is called Onx Hunt. Actually more of a membership. If you download the app you get a free 7 day trial I think. At least you could check it out and see if it's for you before spending the money. After that the app shuts down and it's a yearly fee to activate again. I think around $30/yr for one state and $100/yr for all 50. Paying the money buys you a "membership" which reactivates the app for a year and gives you a password to use their online version on a computer browser.
It's useful! Yes, going to county websites or courthouses gives you the same info, often for free. But it's nice to just put it all in a map, Google maps style. No worries about county boundaries and all that fun.
