In 2006, the National Park Service (NPS) (defendant) adopted a management plan (plan) for the Grand Canyon National Park. The plan authorized motorized-raft use in the park’s Colorado River Corridor (corridor), based on an NPS finding that commercial motorized-raft services were necessary and appropriate to assist park visitors. The plan also decreased commercial-user days to 115,500, increased non-commercial-user days to 113,486, and created a lottery system that favored private boaters without a permit. A coalition of organizations that included the River Runners for Wilderness (plaintiffs) sued the NPS, claiming that the plan was arbitrary and capricious under the Administrative Procedure Act (APA) because it violated the NPS’s 2001 management policies (policies), the National Park Service Concessions Management and Improvement Act (CMIA), and the National Park Service Organic Act (NPSOA). The district court granted summary judgment for the defendants. The plaintiffs appealed, arguing that the NPS had designated the park as potential wilderness, that the policies contained language requiring the maintenance of the park’s wilderness character, and that the plan was inconsistent with earlier NPS decisions to eliminate motorized boating in the corridor. Regarding the CMIA, the plaintiffs argued that the NPS had failed to determine that commercial motorized-raft services were necessary and appropriate for public use. Regarding the NPSOA, the plaintiffs argued that the plan limited public access to the corridor by favoring commercial users over non-commercial users, and that the NPS had improperly found that motorized rafts, when considered cumulatively with other types of noise, did not impair the park’s natural soundscape.