Who was the U.S. senator that sponsored the construction of Mount Rushmore ?
" Rushmore " ( LSD-47 ) was laid down on 9 November 1987 , by the Avondale Shipyards , New Orleans ; launched on 6 May 1989 , sponsored by Mrs. Meredith Brokaw , wife of NBC News anchorman Tom Brokaw ; and commissioned on 1 June 1991 , at New Orleans .