Nuevo León Highpoint -
(Uncertain) - c. 3700 m (12140 ft)
Summit NOT reached!!
I am not sure if the exact high point is known for sure, as the Mexican geographic surveys aren't all that great, including specifying the exact location of the state border.
Nuevo Leon Adventure Company,
http://www.nuevoleonadventures.com/highest-peaks.htm, lists "some of the
highest peaks in Nuevo Leon" as:
Cerro El Morro...12,171'
Cerro El Potosí...12,139'
Picacho San Onofre...11,614'
Sierra El Viejo...11,482'
Sierra Potero de Abrego...11,351'
Sierra Los Toros...10,498'
According to Any Martin, 1991, Cerro el Potosi at 3700 m is thought to be the highpoint, but uncertain ("C") if this is correct for sure. Another possibility listed is a point on the flank of Sierra de la Martha, this being especially uncertain and very dependent on where the exact state boundary lies.
This SummitPost page, http://www.summitpost.org/mountain/rock/152142/el-potos-.html, says that El Potosí is the true highpoint.
PeakBagger, http://www.peakbagger.com/peak.aspx?pid=7983, says the high point is Sierra de la Marta, 3700 m, at 25° 12' N 100° 22' W.
PeakBagger, http://www.peakbagger.com/peak.aspx?pid=7982, says that Cerro El Morro is in Coahuila, 3700 m, at 25° 13' N 100° 24' W. Andy Martin (http://americasroof.com/mexico.shtml) says that the Coahila highpoint (certainty "B") is possibly Cerro El Morro, 3700 m, on map G14C45, although it does list another point in Coahila as the presumed highpoint.
Wikipedia, http://en.wikipedia.org/wiki/Cerro_Potos%C3%AD, 21 Feb 2007, says: Cerro Potosí is the highest mountain in the Sierra Madre Oriental mountain range of northeast Mexico. Access was very difficult in the past, but in the 1960s a microwave relay station was built on the summit, with the road built for this providing easy access from the east. 24°52′N 100°24′W, 3,713 metres (12,181 feet). (I think this road is visible on Google Earth).
References
http://americasroof.com/mexico.shtml - Andy Martin's list.