What is the largest concencrete structure in US?

The largest concrete structure in the United States is the Grand Coulee Dam, located in Washington State. It is the largest concrete dam in the world by volume. Constructed between 1933 and 1942, the dam measures 550 feet (168 meters) high and 5,220 feet (1,591 meters) long at the crest. It contains over 12 million cubic yards of concrete and weighs 18 million tons. The Grand Coulee Dam is part of the Columbia Basin Project, providing irrigation, flood control, and hydroelectric power generation for the region. It can generate over 6,800 megawatts of hydroelectricity, making it one of the largest hydroelectric power plants in the United States.