Frédéric Auguste Bartholdi sculpted the statue and he obtained a U.S. patent for the structure. Maurice Koechlin, who was chief engineer of Gustave Eiffel's engineering company and designer of the Eiffel Tower, designed the internal structure. The pedestal was designed by the architect Richard Morris Hunt. Eugène Viollet-le-Duc chose copper in the construction of the statue, and for the adoption of the "repoussé" construction technique, where a malleable metal is hammered on the reverse side.