Most of the people who drive the road come to fish in Lake Edison. The dam was built as part of a flood control and irrigation project involving three major dams. It was all national forest land, but the Forest Service welcomed dams. Exactly the sort of philosophy that drowned Hetch Hetchy Valley. Dams are formed in various ways.
Beavers use sticks.
Some dams are formed by landslides or lava flows. All have the characteristic of altering the local environment. Yet dams created by humans are often hated by other humans. Muir's budding re-awakening to literary and political activity was brought to fruition by Robert Underwood Johnson, editor of Century, one of the most prominent magazines in the country a hundred years ago. The catalyst was their famous camping trip to Tuolumne Meadows in 1889.