The South Cascades...
is a destination that I have had many adventures in but not nearly enough to cover everything there is to see. From Mount Saint Helens National Monument to the majestic beauty of the Mount Adams Wilderness and everything in between, this part of the Cascades in my experience is much less busy than the others. That is not to say it isn't popular, but it is a bit farther for most so the crowds seem to thin out a bit here. Wildernesses in the area consist of the Indian Heaven Wilderness, Trapper Creek Wilderness, of course, the Mount Adams wilderness briefly mentioned before, and my personal favorite, the Goat Rocks Wilderness. There are also a good handful of beautiful waterfalls in the area that could be considered part of the Columbia River Gorge, but to me, they are buried in the South Cascades, so they belong in this category.
A must see sight is of course the magnificent Mount Saint Helens. The drive along Spirit Lake Highway is incredible with this mountain feeling as if it is within arms reach. This road leads to many trails including the one along Coldwater Lake, which is a gorgeous destination in and of itself. Along with this the road also leads to the Johnston Ridge Observatory, a visitor center within the monument. Be sure to check the roads here though. Link to the National Monument website is at the bottom of this page.
FUN FACT: Before its eruption in May of 1980, Mount Saint Helens was 9,677 feet tall (post eruption: approximately 8,300 feet!) Following this massive blast, one of the first plants to naturally recover was the prairie lupine, one of my personal favorite flowers.
Explore the South Cascades:
Below are just general resources to help you find your next adventure. This is really just the tip of the iceberg but I hope it helps. The camping listed is really just general campgrounds although there is a lot of dispersed and backpacking in the area that can be found with a google search and in several books!