Roosevelt Reservoir on Salt River

Theodore Roosevelt Dam

was constructed in 1911 as the world’s largest cyclopean-masonry dam, built of huge, irregular blocks. These were covered by concrete in a 1996 renovation which also raised the dam by 77 feet. The dam may be viewed from two sites on State Route 88, the Apache Trail. Inspiration Point is upstream of the dam and the Theodore Roosevelt Dam overlook provides a look up the canyon at downstream side of the dam. Roosevelt Reservoir is 21,493 acres at full pool. The reservoir has two arms, one on Tonto Creek and the other along the Salt River. Recreation areas are managed by the Tonto National Forest, which has a visitor center overlooking the lake. The lake is spanned upstream of the dam by the Roosevelt Lake bridge on State Route 188 the longest single-span steel arch bridge in North America. The distinctive arch bridge is 1,080 feet long and 300 feet above the water. When viewed from the side, the bridge deck is slightly arched so drivers would not have the perception that the bridge is sagging. Salt River Project is the operating entity for the dam and reservoir. At the upper end of the reservoir, the Roosevelt Diversion Dam (N33ᵒ38’ W110ᵒ56’) was constructed in 1906 to send water to the Power Canal. The Power Canal extended 20 miles to Theodore Roosevelt Dam, and provided water for hydroelectric generation to power the equipment used to build the dam. The Arizona National Scenic Trail crosses the reservoir on the State Route 188 Roosevelt Lake bridge.

Coordinates: N33ᵒ40’ W111ᵒ10’ (dam)

Ecoregion: Arizona Mountain Forests (World Wildlife Fund); Upland/Eastern Sonoran Mountains (EPA).

Owner: US Bureau of Reclamation, operated by Salt River Project

Pueblo Grande National Historic Landmark

Pueblo Grande Museum and Archaeological Park

is on Washington Street between 44^th and 48^th Streets near the Sky Harbor International Airport. The site contains a platform mound that was originally three stories tall and at the center of the largest irrigation system in the New World between 600 and 1450 CE. Pueblo Grande was the starting point for ten major canals which extended from the Salt River throughout the present-day Phoenix metropolitan area. Additional platform mounds were located at three-mile intervals along other canals. The site of Pueblo Grande itself extended for one mile north of the Grand Canal. The first canals were built between 450 and 750 CE. As the civilization grew, canals were expanded and ballcourts were introduced between 750 and 900 CE. A small circular mound was built between 900 and 150 CE, followed by the larger platform mound and astronomical observatories between 1150 and 1450 CE. Estimated population of the prehistoric civilization at the site of present-day Phoenix was 25,000 to 50,000.

Ecoregion: Sonoran Desert (World Wildlife Fund); Middle Gila/Salt River Floodplains of Sonoran Basin and Range (EPA)

Location: City of Phoenix, Arizona N33ᵒ27’ W111ᵒ59’