Transactions of the American Society of Civil Engineers, Vol. LXVIII, September 1910: The New York Tunnel Extension of the Pennsylvania Railroad, The North River Division. Paper No. 1151 is a comprehensive and detailed technical account documenting one of the most ambitious and significant engineering projects of the early twentieth century. Authored by C. M. Jacobs and presented to the American Society of Civil Engineers, this volume meticulously chronicles the conception, design, and construction of the North River Division of the Pennsylvania Railroad’s New York Tunnel Extension—a monumental undertaking that connected New Jersey and Manhattan via a series of tunnels beneath the Hudson River. The book delves into the historical context and necessity for the tunnel extension, outlining the challenges faced by the Pennsylvania Railroad in providing direct rail access to Manhattan. It provides an in-depth analysis of the engineering problems encountered, including the complexities of tunneling under the riverbed, dealing with high water pressure, and ensuring the safety and stability of the tunnels. The narrative is richly supplemented with technical drawings, diagrams, and photographs that illustrate the innovative construction methods and machinery employed, such as shield-driven tunneling and compressed air techniques. Detailed descriptions of the tunnel alignment, the geological conditions encountered, and the solutions devised for ventilation, drainage, and structural integrity are presented with clarity and precision. The book also covers the logistical and organizational aspects of the project, highlighting the coordination required among engineers, contractors, and workers to achieve timely and successful completion. In addition to its technical content, the volume reflects on the broader significance of the project for urban transportation and the growth of New York City, emphasizing the transformative impact of the tunnel extension on regional connectivity and commerce. The work stands as a testament to the ingenuity and perseverance of early twentieth-century civil engineers and remains an invaluable resource for historians, engineers, and anyone interested in the history of infrastructure and urban development.