+100 to this. Because Yosemite keeps getting called out, I would also mention that Sequoia/Kings Canyon National Park is right next to Yosemite, just as spectacular in many ways (e.g., Rae Lakes Loop), and far less crowded.
If you are fit, you can absolutely do this. In fact, you can go all the way to the other rim and back (rim-to-rim-to-rim). The current record is sub 6 hrs by Ultrarunner Jim Walmsley. [0]
I mostly agree with this, but... if you're a hiker or a trail runner the alps really are amazing, and the infrastructure is far better than in the States. Once you get outside of really built up places like Yosemite Valley, the trails in the US basically are out in the middle of nowhere and so you're carrying all your stuff. For example, if you do John Muir Trail, there's basically nothing between Muir Trail Ranch and Whitney Portal, so you're looking at 100+ miles of carrying your own stuff.
By contrast, many European trails have huts/refugios every 10 or so miles, so you can stop and get a coffee or a meal, or even stay the night. This means that not only do you not need to carry a lot of food you may not even need to carry your own shelter, which lowers the weight considerably. There is some stuff like this in the US, for instance the High Sierra Camps [0], but it's not the norm and it's not cheap (~200 USD/night).
Alps is probably the only real "mogging" of the US (and things like the Himalayas, etc) - we have "one" real impressive mountain range and it has an entirely different feel, being relatively isolated from humans.
Europe and Asia have had tens of thousands of years to make alpine mountains inhabitable, and it shows.
But outside of that, the US has amazing diversity partially because it's basically an entire continent, but also because of an accident of settlement and weather patterns that large swaths of the west were available to preserve.
There was an article recently about how in the UK it's all about restoration because everything is or was inhabited, but in the US it's about preservation because so much was simply never developed at all.
For many of us who backpack in the US for long distances and many days at the time, the remoteness is exactly the point. The lack of those huts/refugios is one of the primary drivers for why OP's friend said what they said.
> In Yosemite, all you have to do is outhike the "Reebok hikers" as we called them back then. An hour's serious walk gives you relative solitude.
You actually don't even need to do this if you park somewhere other than Yosemite Valley. For example, Tenaya Lake is nice and not that far in on Tioga Road.
There's a statistic that floats around which may be apocryphal - something like 90% of visitors to national parks don't get more than a 5-15 minute walk from the parking lot (and some literally never leave the car).
National parks are huge and you can quickly literally get lost forever in them (which is an actual danger, stay on the trails!) if you're willing to walk.
Some of them have very obvious "goals" to see (the geyser, the half-dome) which of course are high traffic, but others are beautiful "all over" and taking the treks is worth it.
I don't know Yellowstone, but the situation with Yosemite is a bit complicated. There are basically two congestion issues:
1. Congestion in the park itself.
2. Traffic.
Yosemite is huge, but the only places that are really built out are Yosemite Valley (where most people go) and Tuolomne Meadows (where a lot of climbers go). Most of Yosemite is backcountry and just accessible by foot. So what happens is that most people go to one of these two places (which, to be clear, really are spectacular) and then stay within a few km radius of the parking lot, hence the crowding. But once you get outside that, it's quite empty. I've done 50-odd mile loops in Yosemite and seen basically nobody [0].
As far as traffic goes, there are very few entrances to the park. If you're coming in from the bay area, you're probably coming in through the Tioga Road/Big Oak Flat entrance. As a result, even if you want to be in some part of the park where there are very few other people, you can end up having to wait in line to enter with the giant mobs of people who want to go to the Valley. The fix here is to enter super early or super late, when there basically is no line.
The problem with the Canyon is that (1) what's really interesting is seeing the whole thing top to bottom and (2) the really spectacular views are when you're partway down, with the best locations depending on the time of day. However, because it's such a challenging hike, most people don't get those experiences. FWIW, Havasupai Gardens is only about halfway down, but because it's the last water tap before the river, it's kind of the last somewhat readily accessible point.
I half agree with the author's take on Yosemite. The valley really is ridiculously overcrowded but the view also is amazing. The situation here is a little bit like the Grand Canyon in that there's lots of amazing stuff but it's more work to get there, mostly in terms of a lot of time on foot. The good news about the Sierras is that except for the amazing big wall stuff in the Yosemite Valley, Sequioa Kings Canyon is basically just as nice and the traffic situation is much better.
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