The dam was a joint project by the Lower Colorado River Authority (LCRA) and the United States Bureau of Reclamation, with partial funding provided by the Public Works Administration.

Originally called Marshall Ford Dam, the name was changed in 1941 in honor of United States Representative J.J. Mansfield.

The concrete gravity dam with embankment wings and saddle dikes was designed to control flooding; to store 1.4 km3 (369 billion US gallons) of water; and to generate hydroelectric power (108 megawatts).

620 was rerouted in 1995 to a four-lane highway bridge on the downstream side of the dam built for increase in traffic due to the popularity in Austin of recreating at Lake Travis.

[2] Lyndon B. Johnson ran for his first elected office as United States Representative for Texas's 10th congressional district (where the Mansfield Dam was located).