The proper name of A Mountain is Tortugas Mountain. It's usually called A Mountain because of a large "A" formed with limestone boulders on the west side. Unlike the Organ Mts. just east, A Mountain is limestone rather than igneous rock. Bishop's Cap, just southwest of the main body of the Organ Mts., is also limestone.

There are two explanations for the "A" on A Mountain. The less interesting is that it stands for "Aggies", the rather unfortunate name of the NMSU athletic teams. The explanation I prefer is that they put the "A" up back in the 1970's and add a letter every time the football team wins.

The southeast side of A Mountain, seen from Bishop's Cap with Las Cruces sprawling beside it, 10/16/05.

The university's observatory on the top of A Mountain, 9/25/04.