From the Super Mario Wiki
The Wild West is a desert like area, filled with oddly green sand and cacti. Pokeys seem to abound in the Wild West and Ostros seem to be the area's main mode of transportation. A small town is also located in the Wild West, having a sheriff's office, a bar and several other buildings in it. The town may have once been a mining community, as a now destroyed, abandoned mine is located near it.