The Surveyor missions were the first attempts by the United States to make soft landings on the moon, and five of the seven spacecraft proved American technology up to the task, including the very first one (Surveyor 1). The Surveyors were originally intended to be their own stand-alone science missions but were quickly folded into support missions for the Apollo program as the space race heated up.
Surveyor 1 marked the first soft landing for the U.S. on June 2, 1966 (four months after Luna 9), but all seven Surveyor spacecraft served to develop and validate NASA’s ability to put a spacecraft on a lunar intercept trajectory, make the proper maneuvers to place a spacecraft at a predetermined point on the lunar surface, and to communicate with mission control on Earth across a quarter-million miles. They also all served as scouts for potential Apollo landing sites. All except Surveyors 2 and 4, that is--those two crashed upon arrival.
Pictured: Surveyor 3.