The Mogollon Rim was formed during the Carboniferous and Permian periods. Those periods mark the end of what they call the Paleozoic Era and lasted from about 358 million years ago to 252 million years ago.
At that time, there was just one big continent on the Earth called Pangea. Much of the world was covered by water. There was a climate change event, and the land dried out quite a bit. This was when Reptiles evolved from the amphibians and dominated the planet.
They think that in addition to the natural change in climate, there was a cataclysmic event. The result was the largest mass extinction in the history of the planet. 90% of aquatic creatures and 70% of land animals died out. It was the only mass extinction of insects that we know of.
Things got crazy. There were volcanoes and earthquakes and giant space rocks slamming into the planet. There were huge fires. Rainforests became deserts. Seas dried up. It took ten million years for life to adapt and recover.
It was one of the dried up seas that left behind the sandstone deposits of the Mogollon rim. Fossilized limestone and crystalline bivalves and corals can be easily found. Some of these corals are the size, shape, and color of a chicken leg.
That's not all the Earth had in store for building the Mogollon Rim. Beginning about six million years ago, a chain of volcanoes sprung up in a line across what is now northern Arizona called the San Francisco Volcano Field. Basaltic lava flowed down over and around parts of the sandstone plateau. Ash covered it's entirety. The area became fertile.
Waterways changed again. The last volcano to blow was Sunset Crater about 950 years years ago. The San Francisco Volcano Field is no longer active. Unlike the volcanoes of the Pacific Rim, which are products of fault lines, They were the result of the continental plates moving over a hot spot in the Earth's magma.The Earth moved on.
The Mogollon Rim Lakes were built in the fifties and sixties for flood management and recreation.