THIS MONTH IN ENGINEERING | October 1904 — when New York went underground

In 1904, New York City opened its first subway line, a 9.1-mile system from City Hall to Harlem that carried 100,000 people on its very first day. The mayor drove the ceremonial train before the system opened to the public that evening.

The achievement was staggering. Built in just 1,275 days at a cost of $40 million, the Interborough Rapid Transit became the largest construction effort the city had ever seen. On peak days more than 12,000 workers were underground, carving through dense streets and rock. An average of 4,600 men labored daily, and 120 lives were lost delivering the system.

Behind it stood two unlikely partners. John B. McDonald, a contractor with no formal engineering education, built his reputation on railroads, bridges, and tunnels, becoming one of the most capable builders of his time. August Belmont Jr., a Harvard-educated financier, provided the capital and organization that turned vision into reality. Together, they delivered a project that redefined modern infrastructure.

The technical challenges were unlike anything attempted in America. Engineers designed shafts and fans to move air through deep tunnels, replaced steam with electric traction to keep passengers safe from smoke, implemented large-scale waterproofing to contain groundwater, and advanced fire safety through early egress planning. Every modern system of mechanical, electrical, hydraulic, and fire engineering traces some lineage to what was tested here first.

When it opened, the subway included 28 stations and 400 cars. Express trains reached 45 miles per hour, with peak-hour headways of three to four minutes. Designed for 200 million riders annually, it immediately set a global benchmark for urban transport.

120 years later, New York’s subway still runs 24 hours a day, carrying more than 5 million passengers daily. Its chandeliers have been replaced by fluorescents, but the system remains one of the most influential engineering achievements of the modern world.

The lesson is clear: the problems of ventilation, power resilience, water management, and fire safety that we wrestle with today are the same questions our predecessors were solving underground in 1904.

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