Well, I was just doing my AP US History notes when I read something about this place. Here's the excerpt:
Echo Park is a spectacular valley in the Dinosaur National Monument, on the border between Utah and Colorado, near the southern border of Wyoming. IN the early 1950s, the Bureau of Reclamation--which had been created early in the century to encourage irrigation, develop electric power, and increase water supplies--proposed building a dam across the Green River, which runs through Echo Valley, so as to create a lake for recreation and a source of hydroelectric power. The American environmental movement had been relatively quiet quiet since its searing defeat early in the century in its effort to stop a similar dam in the Hetch Hetchy Valley at Yosemite National Park. But the Echo Park proposal helped rouse it from its slumber.
In 1950, Bernard DeVoto--a well-known writer and a great champion of the American West--published an essay in The Saturday Evening Post entitled "Shall We Let Them Ruin Our National Parks?" It had a sensational impact, arousing opposition to the Echo Valley dam from many areas of the country, The Sierra Club, relatively obscure in the previous decades, was roused into action... By the mid-1950s, a large coalition of environmentalists, naturalists, and wilderness vacationers had been mobilized in opposition to the dam, and in 1956 Congress--bowing to the public pressure--blocked the project and preserved Echo Park in its natural state.
Pretty cool, huh! The Green River is the river you see running through the center of the first photo. Here's a more up-close photo.
Nothing short of magnificent, no? This would have made the Western barriers of the Great Valley.
And no, I don't believe that the Great Valley actually exists or is actually based on this place. It's just something interesting for fanfic writers, readers, and naturalists. It's just something interesting I've found--nothing more.
(Btw, I just visited the Smithsonian Aviation Institute with my marching band. It was pretty awesome. My friend and I were basically serving as tour guides for everyone. There are a few particular planes that I'm planning on using in my fanfic, and I was absolutely delighted to see them up close. They even have a ME-163 Komet! Can you believe it? Too bad they didn't have any IL-2s or Mosquitoes (or a P-38 with a 20mm cannon for that matter...). Those were my favorites.)