One of the highlights of the California Master Gardener Conference I just spoke at was a lecture by Toby O’Geen, Ph.D., Assistant Soil Resource Specialist at UC Extension. O’Geen mentioned an amazing online soil resource called SoilWeb, avaliable at http://casoilresource.lawr.ucdavis.edu/drupal/node/902.
SoilWeb overlays detailed soil information on Google Maps and Google Earth. There’s even a SoilWeb iPhone app allowing you to use the GPS capabilities of your phone to assist in shopping for, say, the perfect vineyard location.
SoilWeb maps cover most, but not all, areas of the US (Los Angeles isn’t included for some reason). While highly technical, terms are explained via hyperlinks. You click on the table to the right of the map for more detailed information including suitability for farming.
Of course in urban areas you never know what unpleasant surprises lurk beneath the surface such as concrete chunks and lead. SoilWeb won’t tip you off to those things, but it does give a good overall picture of the kind of soil you’ll be dealing with.