If you’ve ever looked at a 3-D relief map of North America, you’ll notice in the far western U.S. and Canada, a chain of wall-like mountains that runs north-south several hundred miles from the coast. In California, its called the Sierra Nevada until somewhere in the far northern part of the state it becomes the Cascade Range. While the Sierras and the Cascades are different types of mountains (e.g., the Cascades are largely volcanic and the Sierras aren’t), they blend into one another in Northern California so they appear to be one range. Thus, when the first Europeans explored and mapped the region, how and why did they distinguish between the two ranges?
Typically, Mt Lasson is considered the southern most point of the volcanic Cascades … although the area is more complicated than just a simple division … where the Klamath, Siskiyou, Trinity, Sierra and Cascade Mountains are divided is more art than science …
While cartography and naming can be a bit ambiguous the change becomes quite clear around Mt Shasta.
To the north you have a range dominated by volcanoes, where to the south you have the grand U shaped valleys that were produced during the Pleistocene Ice Age.
I assume you are looking at something like google earth, if you search Lassen Peak, note how it looks like a volcano. If you look to the South it will be almost purely glacial uplift mountains with no volcanoes.
I should note that the changes are much more obvious when you are actually there in person.
At an wider angle they along with the Rockies and the ranges South through South America are part of the American Cordillera.
The “Sierra Nevada” tag was originally applied by João Cabrilho to the Santa Cruz Mountains in November of 1542. The eventual designation of the mountains that run from Tejon Pass to near Lassen Peak as “un gran sierra nevada” was made in 1776 by Pedro Font, who saw the range from near the mouth of the Sacramento River, and affixed the name Sierra Nevada to them on a map he made that year. He concluded that the mountains found by Francisco Garces to the south (located east from what is now Bakersfield) were the same range. Later writers (early 1800s) talked about finding a way around the Sierra to the north, where the mountains appeared to get lower. I’m not aware if the Spanish/Mexicans in the northern Sacramento Valley considered Mt. Lassen part of the same “range” or not.
It should be noted, that, so far as I know, when Peter Ogden came to California in 1829, he did so via the Pit River, and did not consider himself to have crossed the Sierra.
The name Sierra Nevada was first applied to the mountain range in 1776, by a Spanish missionary who viewed them from near San Francisco.
The Cascades acquired their name in the early 1800s from the cascades on the Columbia River where it passed through the range, mostly explored by American and English explorers.
Really, they could just as well have been considered a single named range. Different names were applied in the south by the Spanish and in the North by English speakers, and the names stuck. The Rockies in contrast have a single name even though there are some large gaps between some of the various ranges that make them up.
I dont know how the first European settlers could tell the difference, but today the boundary is commonly known to be Fredonyer Pass, generally based on type of rock at the surface:
Fredonyer Pass is part of the approximate boundary between the Sierra Nevada and the Cascade Range. This irregular boundary is sometimes defined as the southern extent of Cenozoic igneous surface rock from the Cascade Range. This boundary roughly follows the drainage of the North Fork of the Feather River southeast to Fredonyer Pass. Note that there are other Cenozoic igneous rocks in the Sierra (e.g., near Lake Tahoe), but there is a clear geological division near Fredonyer Pass, and points westward as far as the Sacramento Valley.
Also, the Sutter Buttes, just north of Sacramento, are sometimes considered part of the Cascades.
They really are quite different geologically and geographically. The Sierras are a tilted fault block, with exposed granite and older metamorphic rocks. They have a long, gentle western slope and a steep eastern slope. The Cascades are a string of large volcanic cones surrounded by old lava flows; the topography is nothing like the Sierra fault block. They may be physically aligned, but they area obviously two different landforms.
Thanks for the answers.
Also, could the mods please correct the title of this thread? I made a mistake when I tried to change it and didn’t notice it until it was too late. It should read: "The Sierras and the Cascades–how did they determine the “border” between them?"
Fixed.
On that article, follow the geographical coordinates link to GeoHack - Fredonyer Pass and select the Terrain view. When you’re zoomed in enough to see the terrain forms, but zoomed out enough to see the wider area, the stark differences in terrain north and south of the pass will be very apparent to the eye.
It appears there were no rules regarding the naming of mountain ranges. In fact, they didn’t seem to bother in some cases. Near the coast of British Columbia, Yukon, and the Alaska panhandle, there’s a long range of mountains that are up to 13,000 feet high. However, there’s no name for them taken from the First Nation people or the European explorers. Just the generic “Coast Mountains”. Sometimes I think there should be a vote or contest in B.C. to give this mountain range a real memorable name.
While the “break” point between the Sierra and the Cascade Range might not be obvious from the West, it’s much more obvious from the East. South of the gap that leads to Fredonyer Pass, the “edge” of the mountains on the eastern side retains the usual Sierra thrust fault look (with some small areas of exception, such as just NW of Reno). To the north of that gap, the “edge” of the mountains is much more chaotic, and does not appear as a defined ridge. This reflects the volcanic origin, rather than the tilted block origin.
You see the natural end of the Sierra in the South the same way. The very sharply defined edge to the range south of Tehachapi Pass is still present, though it curves to the west a bit (just as the northern boundary curves west into the gap at Fredonyer Pass). Then, all of a sudden, there is a low gap in the mountains, where CA 136 heads up to meet I-5 at Gorman. To the south of this, the mountains execute a sudden bend, and there is a strong ridge running WNW to ESE: the San Gabriel Mountains. In this case, the boundary is much clearer.
What’s worse, this is just one of 3 coast ranges in that part of the world. There’s the coast range of CA (sometimes split into N and S parts), the coast range of OR (which actually extends into WA). The Olympic Mountains in WA are a “coast range” but somehow got their own name. Ditto the Klamath Mountains in OR/CA.
There’s also some coastal ranges in S. CA that have their own names.
My understanding is that we try to separate the different mountain ranges by how they where formed … the Sierras are a granitic batholith, the Cascades are a volcanic arc, the Klamath, Trinity and Olympics were Pacific islands that accreted to the North American plate … the Coast Ranges are a former forearc feature of the Farallones Subduction … there’s quite the variety of named ridge lines associated with the Rocky Mountains …
I know that’s the case now but these mountain ranges were all named hundreds of years ago before much of the advances in geological science were made.
Also, I’m convinced more than ever that a mountain range with at least one peak that’s more than 1 km tall should have a name other than “coastal range” or “coastal mountains”. It’s like they didn’t even try.
ِAll this geology talk is catnip to me. 
Keep it up!
For what it is worth, the United States Board on Geographic Names and the United States Geological Survey do keep track of names like “Sierra Nevada” and “Cascade Range”, but do not define their extent. The extent of these ranges is, thus, a purely private determination, about which there can be dispute.
The geology of the northernmost part of California, from the coast almost all the way to the border with Nevada, is quite complex. A lot of it is mountainous, including the Trinity Alps, the Cascades, the northern Sierra Nevada, and various coastal ranges that aren’t specifically named. I’m not sure that the average 19th Century dweller in the region was too concerned about where the “Sierra Nevada” “ended”, and where the Cascades “started”. That was more a dispute among geologists. As watchwolf and others have noted, it’s mostly a matter of the underlying geological processes that leads geologists to set the boundaries. Sometimes, those boundaries aren’t obvious.
For example, there is a group of mountains north of Bridgeport, CA, called the Sweetwater Mountains. Viewed from the south or the north of them, they appear to be essentially part of the Sierra Nevada, separated only by the narrow Hells Gate in the south, and the cañon of the West Walker River in the north. However, as much as they look like they are part of the Sierra, they are not considered part of that range geologically. This is due to the processes creating them being different. But I doubt that travelers at the time considered them different entities.
OTOH, the EPA has divided (and subdivided …) the US into Ecological Regions, two of which are the Cascades and the Sierra Nevada.
Feel free to check to see how well those match anyone’s concept of the extent of those mountains. Probably not a great match*, OTOH the divisions are fairly finely made.
But the visible difference in vegetation might have counted a lot to settlers.
- E.g., they have one nearly continuous coast mountain region from near Santa Cruz up to the Olympic Peninsula. And the “core” Olympic Mountains are a different region, of course.