New York Subway Extension Begins Service

On July 24, 1904, the IRT subway added key Manhattan stations as part of its initial system expansion. Using innovative cast-iron tunnels and third-rail electrification, the project overcame dense urban geology with shield tunneling methods pioneered by chief engineer William Barclay Parsons. The extension carried thousands of daily passengers on steel-bodied cars, easing streetcar congestion and fueling skyscraper growth. Its success validated public-private partnerships in urban rail and set standards for rapid transit worldwide, influencing subway designs from London to Tokyo.