The name was recently changed from "Ninham" to "Nimham" to correct a long-standing spelling error.

In 1940, the Civilian Conservation Corps Camp P-135 of Peekskill constructed an 82-foot-6-inch-tall (25.15 m) International Derrick steel fire lookout tower on the mountain.

The tower was officially closed in early 1989 by the New York State Department of Environmental Conservation.

The restoration work was completed in Spring 2005, with an official dedication ceremony on July 24, 2005.

The tower appears on the National Historic Lookout Register; it is one of only a few towers in New York that still has the manufacturers identification tag, which reads: "THE INTERNATIONAL DERRICK & EQUIPMENT Company (IDECO) Columbus, Ohio - Los Angeles.