It doesn't even need to be a mountaintop as is the case with Ludington pumped storage in Michigan. Another thing is transmission. If you have a lot of sun it doesn't mean everyone does. It's darker to the west as the sun rises. Building wires from generation in one place to load somewhere else has a long history. It's still a question of money. Want to move power from Ohio to Indiana? Ok. Want to move it from Ohio to Oregon? Unlikely.
Of course I don't think that we will be transmitting electricity over long distances, ever. Physics just says No to that. But our current model of power generation being one big polluting building, is a relic of the Industrial Revolution, and no longer appropriate to the Space Age we live in. We need multiple sources of power working together, and distributed much more liberally across the country. With solar, wind, hydro, nuclear, battery, and clever storage solutions (like pumping water uphill, steam generation, etc.), all playing a role in power generation/storage everywhere. The only thing holding us back from this, is our fucking horrendous power grid. Fuck... let's take 30% of the Defense Budget and throw it into modernizing the entire energy grid across the USA, and training all the hundreds of thousands of people who will install, operate, service, and manage it. Heh... yeah right. These motherfuckers still think there was a child sex ring in the basement of a pizza parlor... that didn't have a basement. Good fucking luck on them ever giving in to a "socialist" program like modernizing the energy grid... America is fucked.