Newcomb's snail is endemic and restricted to the island of Kauaʻi. A number of very large watersheds traverse the southeast quadrant of the Kauaʻi island, including Olokele Stream, Hanapēpē Stream and Waimea River, all of which have numerous tributaries. No recent surveys for Newcomb's snails have been undertaken in the Hanapēpē watershed, or in any of the large neighboring stream systems, because they are located on privately owned lands and are difficult to reach because of the rough terrain. It is possible that Newcomb's snail populations remain in that region of Kauaʻi.