Black Chamber

The Black Chamber was a decryption office that operated from brownstone buildings on 37th and 38th Streets, processing intercepted diplomatic messages. The team analyzed codes from telegraph cables, diplomatic wires, and written documents sent by foreign governments.

Herbert Yardley founded this intelligence operation in 1919 to address the challenges revealed during World War I. The office focused on decoding foreign communications during the unstable years that followed the conflict.

The office marked the beginning of organized peacetime cryptanalysis in the nation, setting standards for future intelligence operations. This approach to message surveillance later became a model for many national security agencies.

The office was located in an urban setting but was not open to the public, as it operated as a secret intelligence agency. Visitors today can only view the exterior of the buildings or learn about the site through historical accounts.

The office maintained direct partnerships with telegraph companies and accessed foreign embassy communications through Western Union. This secret arrangement with private businesses was an early example of intelligence agencies using commercial channels for data collection.