The Pit River Bridge is a double deck, deck truss, road and rail bridge over Shasta Lake in Shasta County, California. The bridge, carrying Interstate 5 on its upper deck and Union Pacific Railroad on its lower deck, was built in 1942 as part of the construction of the Shasta Dam/Shasta Lake reservoir system. The Pit River Bridge was constructed to replace the Lower Pit River Bridge, as the rising waters of the Shasta Lake reservoir would have put the older bridge underwater. The entire bridge spans 3,588 feet (1,094 m) long on the upper deck and 2,754 feet (839 m) on the lower deck. With a height of 500 feet (150 m) above the old Pit River bed, it is structurally the highest double decked bridge in the United States; however, today the bridge sits only about 40 feet (12 m) above the water when Shasta Lake is full.