The Demolition of Hell Gate

When the authorities discerned the existence of the Deep One's Lair under Hell Gate, they demolished Y’ha-nthlei with 300,000 pounds of explosive, "the largest planned explosion before testing began with the atomic bomb". The destruction of Y’ha-nthlei forced the Deep Ones there northward to Innsmouth on the Massachusetts's coast, joining with or perhaps conquering the Deep Ones on Devil's Reef summoned by Captain Obed Marsh, who died in 1878.