Tonto Natural Bridge, Natural arch in Gila County, Arizona

Tonto Natural Bridge is a travertine arch spanning Pine Creek with caves and alcoves formed beneath its span. Water continuously flows over the limestone, creating an active geological formation that changes over time.

Scotsman David Gowan first documented the bridge in 1877 while hiding from Apache groups, then tried to claim the land under squatter's rights. His family lived near the bridge until 1948, and their lodge building still stands and is listed on the National Register of Historic Places. Glen L. Randall of Pine bought the bridge and 160 surrounding acres that year; after his death in 1967 his widow Eloise sold the property, which became a state park.

The Gowan family's lodge, built near the bridge and lived in until 1948, is listed on the National Register of Historic Places. It is the structure the sources call the lodge; no "Goodfellow Lodge" exists at the site. The building was repaired after the park's 2010 budget crisis.

The park has four marked trails suited to different hiking levels, allowing visitors to explore at their own pace. Pets and glass containers are not permitted to protect the area and other visitors.

Ferns and other plants grow inside the caves beneath the arch, thriving in the moist, shaded environment. This small ecosystem shows how life persists in the hidden pockets of the formation.