Quote Originally Posted by ranger View Post
I was reading a-lot of the native americans that built into the sides of things like the Anasazi had their crops on top of the mesas as it was fairly fertile land to grow crops on with fairly decent water/snow. http://www.nps.gov/meve/forteachers/..._puebloans.pdf
It depends on the size of the mesa; smaller mesas (what are generally called buttes) will tend to have less soil, which means less vegetation, which means less fertile soils. A true mesa can be many miles across, meaning that you may not even be able to tell it's a mesa when you're up top. Mesa Verde, for example, is a bit more than 10 miles across. A lot of cliff dwelling weren't on mesas, but just canyon walls (e.g. Montezuma Castle). The edges of the Colorado Plateau are littered with them.

There are also some impressive dwellings in the same vein that aren't based on cliffs at all (e.g. Casa Grande and pretty much all of Central America). They were a little outside the scope of the discussion, though.