Echo Park Dam was proposed in the 1950s by the U.S. Bureau of Reclamation as a central feature of the Colorado River Storage Project.

The Echo Park project was abandoned in favor of Glen Canyon Dam on the main stem of the Colorado, in lands that were not at that time protected.

The monument was expanded in 1938 to 200,000 acres (81,000 ha), encompassing the canyon networks of the Green and Yampa upstream from the dinosaur quarry.

"[3] Implicitly comparing the flooding of Echo Park to the Hetch Hetchy intrusion in Yosemite, the article was picked up by Reader's Digest and saw wide circulation.

The proposal was whittled down by excluding grazing lands, and then by intervention by Utah, favoring the reservation of Glen Canyon as a reservoir site.

A 1946 survey of potential recreational resources undertaken by the National Park Service in the Colorado Basin entirely omits the Glen Canyon region from its assessment, focusing instead on the Aquarius Plateau to the northwest and Monument Valley to the southeast.

[11] Echo Park Dam was planned for a site just downstream from Steamboat Rock, a monolith standing just below the confluence of the Green and Yampa, where the Green flows out of Echo Park, a broad wooded flatland walled by steep canyon cliffs.

[11] Roughly half of Steamboat Rock's height would have been underwater, along with archeological sites, caves and wilderness valleys.

Although Split Mountain Dam was to have a hydraulic height of about 100 feet (30 m), a 9,000-foot (2,700 m) penstock was planned to be built to carry water across a deep bend of the Green, taking advantage of the river's fall to create a 200-foot (61 m) head for power generation.