The first underground segment of the New York City Subway opened, connecting New York City Hall (station pictured) with Harlem.

The first regularly operated line of the New York City Subway opened on October 27, 1904, and was operated by the Interborough Rapid Transit Company (IRT). The early IRT system consisted of a single trunk line running south from 96th Street in Manhattan, with a southern branch to Brooklyn. North of 96th Street, the line had three northern branches in Upper Manhattan and the Bronx. The system had four tracks between Brooklyn Bridge–City Hall and 96th Street, allowing for local and express service. The original line and early extensions consisted of:

• The IRT Eastern Parkway Line, running between Atlantic Avenue–Barclays Center and Borough Hall
• The IRT Lexington Avenue Line, running between Borough Hall and Grand Central–42nd Street
• The IRT 42nd Street Shuttle running between Grand Central–42nd Street and Times Square
• The IRT Broadway–Seventh Avenue Line, running between Times Square and Van Cortlandt Park–242nd Street
• The IRT Lenox Avenue Line, running betwern 96th Street and 145th Street
• The IRT White Plains Road Line, running between 142nd Street Junction and 180th Street–Bronx Park