a film by Kerry Michaels and Stuart Math, Direct Cinema, 28 mins., $24.95 . CODE: DCV-4

River of Steel is an engaging, concise film “about how the New York City subway system was built, and how it came to redefine the very meaning of urban scale.” That’s a lot of ground to cover in less than half an hour, and the latter issue is just touched on rather than fully investigated. But the filmmakers make their point: Modern New York simply would not have been possible without its subways.

Entrepreneurs began work on primitive systems in the 1870s, and there were several false starts. Finally in 1900 the former mayor Abram S. Hewitt set up the successful Interborough Rapid Transit Company. The ensuing construction was an immense undertaking, as the movie makes clear. The IRT and its eight thousand workers had to deal with “strikes, lawsuits, cave-ins, even quicksand.” The first line was completed in 1904, and on opening day, 110,000 people rode it. One early passenger must have had a movie camera, for River of Steel treats us to a marvelous engine’s-eye view from an early train as it shudders through a tunnel and out over the Brooklyn Bridge.

The film concludes with a quick discussion of the subway’s expansion into the outer boroughs, citing its effect on the crowds at Coney Island: before the subway about a hundred thousand people gathered there on a typical Sunday; afterward the number swelled to nearly a million. Like those early trains themselves, this film moves along at a fast clip, but it’s a swell ride.