At 770 feet (235 meters) tall, Oroville Dam is the tallest in the US. Built on the Feather River in California, Oroville is an earthfill dam which created Lake Oroville.

Hoover Dam, however is the tallest concrete-gravity arch type of dam. Standing at 726.4 ft (221.4 m) tall Hoover is the second tallest.

Glen Canyon Dam is fourth tallest at 710 ft (220 m).

Grand Coulee Dam is eleventh at only 550 ft (168 m).

More Info: en.m.wikipedia.org