Mutual Reserve Building, Office skyscraper at Broadway and Duane Street in Tribeca, Manhattan, United States.

The Mutual Reserve Building is a 13-story office tower located at Broadway and Duane Street in Tribeca. Its facades feature round-arched arcades and rusticated stone piers clad in limestone and granite.

Completed in 1894, this building was among the first in New York City to use a cage-like steel frame system for skyscraper construction. This innovative structural method became a key development in modern high-rise architecture.

The building's name comes from its first main tenant, the Mutual Reserve Fund Life Association, which went bankrupt in 1909. It was then renamed the Langdon Building after the owner's son. From 1967 to 1980 it housed the New York City Landmarks Preservation Commission, the agency that later designated it a landmark in 2011.

The ground floor holds retail spaces, while upper levels provide office space with marble hallways. Its location at a busy intersection makes the building easy to find and access.

The steel frame was encased in brick and asbestos cement, and the New York Times called the building "absolutely fireproof"; wood was used only for furniture, doors and casement windows. Carnegie Steel engineer C. V. Childs said his wind-bracing system of gusset plates at the narrow end, reducing distortion, was first used here or at the Savoy-Plaza Hotel.