Wertheim National Wildlife Refuge is home to the Long Island National Wildlife Refuge Complex headquarters and visitor center. The Complex consists of seven national wildlife refuges, two refuge sub-units and one wildlife management area. Collectively, the ten units are approximately 6,500 acres in size.

Wertheim is a 2,550 acre refuge on the south shore of Long Island and is bisected by the Carmans River. The Carmans is a New York state designated scenic river and one of the largest on the island. Wertheim hosts a variety of habitats including oak-pine woodlands, grasslands and fresh, brackish and salt water wetlands. These habitats attract and support many types of wildlife including white-tailed deer, osprey, muskrat, fox, turtles, frogs and fish. The refuge also serves as a haven for waterfowl, shorebirds, raptors and songbirds.