Understand
For purposes of this article, the southwestern region is bounded on the:
West, by the Arizona state line;
North, by Interstate 40 on the route of historic Route 66, although a few features south of the highway are considered to be in the northwestern region;
East indistinctly, by the western slopes of the Sacramento Mountains White Sands National Monument is considered to be in the southeastern region;
South, by the Mexican border and Texas state line.
Note, however, that the area around Albuquerque and extending as far south as Socorro is considered to be a separate region, Central New Mexico, rather than part of this one.
This is a geographically complex region that has a great deal in common with the basin-and-range country of Arizona and Nevada from a geological standpoint. Much of it is mountainous, with some comparatively recent volcanism in a few places. The combination of rugged terrain and low rainfall has limited the number and size of cities and towns here, except in the valley of the Rio Grande, which contains most of the region's population, including the comparatively large population about 75,000 community of Las Cruces.
