United States Postal Service
Railway Mail: The United States Railway Mail Service at the New Post Office and Pennsylvania R.R. Station, New York City.
Office of Supt. Railway Mail Service
At the turn of the 20th Century, the Pennsylvania and New York Central Railroads were competing for dominance of New York passenger traffic. The Pennsylvania built Pennsylvania Station in 1907 as part of its Hudson Tunnels project. In conjunction with the station, a large new post office was built and began operation in 1910. This document explains all of the improvements and innovations applied to the structure and how they would speed mail along its way.