The Elevation and Prominence of San Jacinto Peak

I was surprised when I finally made it to the summit of San Jacinto Peak that the sign there said Elevation 10,834 feet, since the USGS Topo map gives 10,804 feet. Surprisingly, apparently neither of those numbers is correct!

Furthermore, strictly speaking, San Jacinto Peak is not the second-highest peak in southern California; it is #7 on that list! However, it is the second-most prominent peak in southern California, and the San Jacinto mountain range is indeed the second-highest mountain range in southern California.

First, the true elevation of the peak itself is apparently 10,842 feet.

This elevation, 10,842 feet, differs from the 10,804 feet, due to three effects:

  1. The elevation for the benchmark on the original USGS quad map was wrong by 27 feet! (I don't know why; if you do, please let me know.)

  2. The change in the lat - lon - elevation datum from NAD27 to WGS84 adds 3 feet at this location.

  3. The elevation on the USGS topo map and the summit sign refers to the USGS benchmark, which is 8 feet below the highest point at the summit.

See also 10,804' or 10,834' and California P 2,000 Summits.

See below for some amusing other information about the elevation of the peak.

Second, San Jacinto Peak is often said to be the second tallest peak in southern California, but that isn't correct; it is the seventh tallest peak in southern California. The correct statement is that if you list only the highest elevation in each separate mountain range in southern California, the San Jacinto Mountains would rank second in highest elevation. (Note that Mt. Whitney is not in southern California; it is in the Sierra Nevada.)

The difference is that there are six mountains in the San Bernardino Mountains, San Gorgonio Peak and five neighboring peaks, that are all taller than San Jacinto Peak. See the full list here (page down about three times to Message #1467).

Elevation is one important quantity, but prominence is more relevant at times since it measures how high a peak is relative to the surrounding terrain. For example, Mount Sunflower, the highest point in Kansas, at 4,039 feet elevation, has a prominence of approximately 20 feet. I.e., the terrain around Mount Sunflower is all at about 4,000 feet elevation, and Mount Sunflower is just a very broad hill that is 20 feet above the surrounding land for as far as the eye can see.

Everyone would agree that prominence is a better measure of how impressive Mount Sunflower is than its elevation. It gets a little trickier for Mount San Gorgonio.

Surprisingly, using a formal definition of prominence as the elevation of a summit relative to the highest point to which one must descend before reascending to a higher summit, San Jacinto Peak is the most prominent summit in southern California! Going by that definition of prominence, San Jacinto Peak, at 8,319 feet, beats out San Gorgonio's 8,282 feet by 37 feet. Mt. Baldy comes in third on that list at the much lower value of 6,224 feet.

This definition of prominence works well when the next higher peak is nearby. In many cases the prominence value is the difference in elevation of the summit relative to the saddle going to a higher summit.

However, the definition of "prominence" is a one-sided measure (measured only in the direction to the next highest peak), and thus cheats the highest peak in southern California, since it is measured relative to the lowest point on the way to the Sierra Nevada. San Gorgonio is more prominent measured relative to Banning Pass than is San Jacinto Peak. Clearly, Banning Pass is a more appropriate reference point for the prominence of San Gorgonio than using some point out in the Mojave Desert halfway to a higher peak in the Sierra Nevada.

Mt. Baldy is also cheated a bit since it is measured relative to the Cajon Summit rather than relative to the Cajon River.

Hence any reasonable person would say that Mount San Gorgonio is indeed the most prominent peak in southern California, with San Jacinto Peak the second most prominent, since the prominence of the higher-elevation bumps next to Mount San Gorgonio is considerably diminished by the presence of Mount San Gorgonio.

So it is perfectly fine with me if you call San Jacinto Peak the second highest mountain in southern California, as long as you mean highest in the sense of prominence, or in the sense of the highest elevation in a separate mountain range. (;-)

More information about reported elevations of San Jacinto Peak

Disclaimer: This page simply reports my investigation into online pages that discuss the elevation and prominence of the peak. I have no special expertise in determining those quantities; I am simply reporting what I have found online.

Go to The San Bernardino and San Jacinto Mountains

Copyright © 2007 by Tom Chester.
Permission is freely granted to reproduce any or all of this page as long as credit is given to me at this source:
Comments and feedback: Tom Chester
Updated 14 August 2007.