Yaphank (/ˈjæpæŋk/) is a hamlet and census-designated place (CDP) in Suffolk County, New York, United States.

In the 1930s, Yaphank was a center of American Nazism where Camp Siegfried drew up to a thousand weekly visitors from New York City for pro-Nazi rallies and vacationing.

[5][6][7] Captain Robert Robinson came to Yaphank and built his Dutch Colonial house with the building dated at 1726.

[8] In the mid-18th century, John Homan built two mills along the Carmans River, which runs directly through the center of the town.

[citation needed] In 1843 the Long Island Rail Road built a railroad station in Yaphank (still named Millville at the time), and nearly overnight the small mill town became a major commercial center.

In 1947, the U.S. Department of War transferred the Camp Upton site to the Atomic Energy Commission, and it now serves as the home of Brookhaven National Laboratory.

Before the end of World War I, more than 30,000 men received their basic training there, including songwriter Irving Berlin.

In 1979, Parr Meadows served as the venue of a tenth-anniversary reunion concert that featured many of the original performers from the Woodstock Festival.

[16] Until 2017, homes in the former Camp Siegfried area, on land that was owned by the German-American Settlement League, were under covenants restricting residents to those of German extraction only.