Topband: Soil conductivity maps

[Jeff Kinzli N6GQ]

So I'm looking to purchase a new QTH. I'm not particular about
location, but would like to optimize for soil conductivity and any
other parameters that would increase near and far field propagation
and minimize ground losses. I've seen the US Gov M3 maps, but they are
very coarse. They also only define conductivity, and I'm wondering
what other quantities would be useful to look at.

I know that a salt water takeoff or marsh is awesome, but that's not
gonna happen in this iteration - looking very much central USA (W5,
TX), inland.

So, any more fine-grained maps available? Or other quantities that
would be worth looking at? Books that discuss this sort of thing?
Mostly for either pinpointing optimal areas, or making sure that a
good looking property is at least half-way decent...

Thanks for any guidance,

de N6GQ