USS Dolphin was the last diesel-electric submarine to serve in active commission with the U.S. Navy.
Dolphin was launched in 1968 and commissioned in 1969 as a research and development submarine. It was the Navy’s final conventionally powered submarine, built after nuclear propulsion had become standard for American attack and ballistic-missile submarines.
The boat supported trials involving sonar, weapons, communications, and other underwater technologies. Its relatively small size and conventional machinery made it useful for experiments that did not require a full-size nuclear submarine.
Dolphin was decommissioned in 2007, ending the U.S. Navy’s active service of diesel-electric submarines. The designation AGSS meant auxiliary research submarine. USS Blueback, sometimes confused with Dolphin, was the Navy’s last diesel-electric submarine before Dolphin entered service, but Dolphin remained active longer.