In a West Side neighborhood long isolated from the rest of Manhattan, crowds gathered on Sunday for a truly rare sight in New York City: the opening of a new subway station. Train aficionados and local families streamed in, squealing in delight and snapping photos of the city’s first new subway station in a quarter century.

As the No. 7 train pulled out of the new Hudson Yards station just after 1 p.m., destined for Times Square, the East Side and finally Queens, it opened a new chapter for the city’s subway system and a signal moment for the neighborhood that the station was built to serve — and that not so long ago was a mostly forgotten, largely industrial pocket of an otherwise bustling borough.

In a city that is in so many ways defined by its subway — the 24-line, 660-mile system records more than five million rides a day — the Far West Side had been one of the few places in Manhattan with no claim to a spot on the city’s subway map. But that changed on Sunday, as did the subway map (which now includes the 469th station), and long before the official opening, the promise of the subway extension lured new development to the area. Today, cranes dot the skyline near the station as buildings rise nearby, and the station’s opening is expected to fuel even more growth.

At a ribbon-cutting ceremony on Sunday morning, at the station entrance at 34th Street near 11th Avenue, Mayor Bill de Blasio called the opening a “monumental day” for the city. The $2.4 billion, 1.5-mile link had been a long time coming, he said, but it was worth the wait.