Cascade-Siskiyou, California

Think green. These mountains receive more than 50 inches of rain a year, which is why their slopes are thickly forested with conifers—perfect habitat for rare species like the Northern Spotted Owl. 

A Cascade-Siskiyou National Monument was established on the Oregon side of the border in 2000; now some environmentalist want to extend it south into California.

The most accessible portion of the existing monument is the Hyatt Lake recreation complex in Oregon.