>>2017253Delineation of the southern Rockies and the basin and range province occurs in northern NM because that's where the main chain ends. Even though there are literally tens of thousands of peaks within the Rockies main chain and tens of thousands of peaks that fall outside of it but have line parents within the main chain of the Rockies. Texas' small mountainous area falls within either the basin and range province or the sierra madre occidental. Similar delineation occurs in the west along the Wasatch range in UT and the entire high country of AZ (and AZ's plateaus which are among the largest high elevation plateaus in North America). Even though almost all of AZ's and UT's thousands of peaks and hundreds of mountain ranges (AZ alone has over 210 mountain ranges and more individual peaks with 300ft+ of prominence than CO) contain line parents in the Colorado Rockies. The OP image only depicts the main chain, the North American Cordillera extends from the equator to the arctic in Alaska and includes the Rockies and all of its tertiary and disjunct ranges in western North America along with the coastal ranges.
