passage of the Federal Aid Highway Act of 1956, bringing into existence the Interstate and Defense Highway System. Several U.S. Highways in Arizona were chosen to become the corridors for the new Interstates, including US 66, which was slated to be replaced by I-40. By December 1960, approximately of US 66 had been rebuilt into the first section of I-40 to open in Arizona, and a further of US 66 was also undergoing conversion into I-40. By October 1962, of US 66 between Williams and Flagstaff was being rebuilt into parts of I-40. The new section was completed and opened to traffic later the same year. In 1966, a new four-lane steel bridge was opened over the Colorado River, replacing the Red Rock Bridge. US 66 was moved onto the new bridge, running concurrently with the new I-40 across the river. The Red Rock Bridge was closed following the opening of the new bridge and sat completely abandoned for over a decade. Unlike the Old Trails Bridge, the Red Rock Bridge would never be repurposed. In 1976, the bridge was entirely dismantled. Today, only concrete pilings remain where the bridge once stood. By September 1967, over of I-40 had been constructed or rebuilt from sections of US 66, with another under way. I-40 around Flagstaff was completed and opened to traffic in 1968, bypassing US 66 and US 89 through town. By 1971, almost all of US 66 east of Flagstaff had been rebuilt into I-40, save for the city streets through Winslow, Joseph City and Holbrook. I-40 had also been completed around Flagstaff and west to the junction between SR 64 and US 66 east of Williams. Another section of I-40 was complete between Seligman and Ash Fork, with a tiny section completed just east of Ash Fork. Almost all US 66 had been converted into I-40 between Kingman and Topock as well, save for a section east of Topock and a section south of Kingman. A small section of I-40 had also been completed between Kingman and a junction with US 93 about south of Hackberry. Controversy came with the construction of I-40. There was a large opposition to freeway bypasses around the towns along the route. Much of the opposition came from town officials and businessmen, all too familiar with the decline of Oatman caused by the 1952 bypass. A large political effort was mounted across several