The occurrence of hurricane landfalls on the United States may be related to alternating intervals of persistent above-average and below-average surface temperature of the North Atlantic Ocean. The cycle of temperature variations, known as the Atlantic Multidecadal Oscillation (AMO), has been identified by study of records based on thermometer readings that go back to the late 1800s. These records do not cover a large enough span of time to adequately test the stability and persistence of the AMO. Better understanding of the AMO and its possible link to hurricane landfalls requires extending our knowledge of the ocean-surface temperature to periods before these thermometer readings were recorded.