Lockheed developed it as a solid fuel Fleet Ballistic Missile (FBM) for the US Navy. The first successful test flight was from Cape Canaveral on January 7, 1960. The nuclear warhead was developed at the (now) Lawrence Livermore National Laboratory by a team headed by Harold Brown from 1957. In July 1960, the Navy accepted delivery of the first 16 warheads and on November 15 the first Polaris missile was test launched from a submarine.
The missile was 12.3 meters (40.5 feet) long and with a finspan of 2.6 meters (8.5 feet) and capable of delivering a 1MT warhead 4000km.
The USS George Washington was the first fleet ballistic missile submarine, carrying sixteen missiles. From 1960 to 1966 a further forty SSBNs were launched.
The British use of Polaris stems from the failure of the Blue Streak missile and the cancellation of the Skybolt project in the 1950s. Harold Macmillan and John F. Kennedy agreed at the 1962 Nassau Conference that the United States would supply Britain with Polaris. America would supply the missiles, the launch tubes and the fire control system, while the warheads and submarines would be British made. In return America was given certain assurances by Britain regarding the use of the missile. The Polaris Sales Agreement was signed on April 6, 1963.
The British polaris submarines were the Resolution Class Ballistic Missile Submarines.
The British upgraded to Trident when it became available.