Rather than being designed as Skipjack class attack submarines with a missile compartment added, the Ethan Allens were designed from scratch as Fleet Balistic Missile (FBM) submarines carrying the Polaris A-2 missile. In the early and mid-1970s, they were upgraded to Polaris A3s. Because they could not be modified to carry the larger diameter Poseidon missile, in the early 1980s they were refitted as SSNs (attack submarines) — fire control systems were removed and the missile tubes were filled with concrete. Two were further converted to carry SEALs, accommodating 67 troops each. The Ethan Allen class submarines were decommissioned between 1983 and 1992. All have now been broken up.
In the Tom Clancy novel Hunt for Red October, Ethan Allen (by now old and ready to be broken up), is detonated near the Red October in order to convince the Soviets that the fictional Typhoon had been destroyed.