At the Base of the Giant's ThroatThere are ninety thousand registered dams in the United States, fifty thousand of them classified as major. Nearly all of this infrastructure was built during a forty year period, from 1932 to 1972, in an era of public investment and political consensus that seems inconceivable today. These incredible structuressometimes called the American Pyramidshelped the country rebound from the Great Depression, brought water and electricity to enormous reaches,