Viewed from the platform of the elevated Dyckman Street station on the 1 train of the New York City subway, it's hard to imagine that the bland, towering concrete apartment building is a monument to Manhattan's final triumph over agrarianism. Glowering over Nagle Avenue and the subway tracks with its Cold War charm, the building sits on what used to be a farm -- the last farm in Manhattan, actually. The site wasn't sold to developers until 1961. Prior to that, the holdout field served as an in-town vegetable provider to the crossroads of the world.

Standing on the platform, a tour guide points out the more comely prewar buildings that spread out from the station like a crazy quilt of brick and stone, all built after the subway first squealed above the neighborhood in 1905.

"The city, particularly the way Manhattan has been developed, is a product of the subway," said subway historian and engineer Joe Cunningham. "It enabled the development of the outer boroughs and allowed the central business district of Manhattan [the area south of Central Park] to develop as it did."

This month, the New York City subway, the catalyst of New York's 20th-century growth, celebrates the 100th anniversary of its opening on Oct. 27. Tours like this one -- which traces the route and history of the first line, 9.1 miles from City Hall to 145th Street in Manhattan, and some of its extensions built north into the Bronx -- are part of a year-long centennial fete put on by New York City Transit. All around the city are looks at the construction, culture and impact of one of the world's most famous subway system:

* A regular calendar of mobile tours, including one in early December that will start in Times Square and explore the 1940 merging of the city's three subway systems into one consolidated public entity.

* At the Transit Museum, in an abandoned Brooklyn Heights subway station, visitors can see a fleet of subway cars gone by, from wooden models to the late, and sometimes lamented, steel Redbirds, each adorned with period advertisements.

* A major 100th anniversary exhibit at the Transit Museum traces the construction of the system, including the story of a worker who was spit up from beneath the riverbed to the surface of the East River when a tunnel collapsed in 1916. (He survived, two others died; imagine the screaming headlines that followed.) The exhibition, titled "The City Beneath Us: Building the New York Subway," also includes social history of the laborers who worked on the project, construction and engineering challenges, and the politics and business surrounding it all.

It's a time to remember the many moods of the system, from the hopeful inaugural train piloted by Mayor George. B. McClellan (it was a half-hour late) through decades of galloping outer-borough growth to the bleak, graffiti-filled 1970s when the tunnels symbolized urban apocalypse in such movies as "The Warriors," "C.H.U.D." and "The Taking of Pelham One Two Three." In recent years, the newly sanitized subway has come to symbolize the rebirth of New York in the Rudy Giuliani era.

But whatever the status of the love-hate-love affair between the city and the city below, through it all the subway has ferried countless passengers on their daily rounds -- currently more than 4.5 million along 722 miles of track. In the course of that century-long chore, it has profoundly altered the urban landscape -- and Cunningham wanted to show us how. The tour started outside the platform on the elevated station at 238th Street in the Bronx, a creaking wooden construction that palpably shakes when trains come through, even on the stairway leading up from the street.

As the 1 train rumbled into the station, we headed downtown. It is an odd way to tour, with regular passengers bounding on and off and no guaranteed seats. But our group -- some singles, a few families and couples, and mostly male specimens of the "rail fan" species -- managed to keep together.

At the elevated station on 225th Street at Broadway, we stood in what physically seemed to be the Bronx -- across the water from the city -- but politically is in the borough of Manhattan. The Army Corps of Engineers' rerouting of Spuyten Duyvil Creek to create the Harlem River Ship Channel is responsible. In the late 19th century, a canal was built to shorten the route from the Hudson River to Long Island Sound, which the subway took advantage of with the construction of a shorter and cheaper bridge.

And that's the story of the subway: change. There was public transit prior to the subway -- elevated locomotives and streetcars plied the city. But passengers who had little use for sooty trains or plodding streetcars surged into the electric-powered, grade-separated subway cars. From 1910 to 1940, the crowded tenements of the Lower East Side that photographer Jacob Riis made the shame of the nation lost 63 percent of their population. Thanks to the mobility offered by the subway, they moved up and out to formerly rural areas. During the same time period, Brooklyn's Coney Island, where the subway opened in 1915, grew by 921 percent.

Standing at the 168th Street station, the evolution of the system stares.

The platforms on each side have at least three different styles, from dignified tile to brutal concrete, for just above was the home of the New York Highlanders, who became the Yankees in 1913. Due to the crowds, the platforms were extended, and extended again. The old stadium site became home to Columbia Presbyterian Hospital (now New York-Presbyterian).

Then there's the dirt. Despite the clean-up of the graffiti-splattered cars, and an overall neater system, New York's subway stations are still pretty dirty compared to Washington's 1970s Metro. Cigarette butts, stray beer cans and the sad remnants of once Happy Meals litter the trackbed.

When a woman on the tour remarks on the filth, especially on the tracks, a fellow tourgoer rejoins in a pronounced outer borough accent, "It's open 24 hours a day, seven days a week. When exactly is the good time to clean it?"

Times Square station is the system's busiest, serving 500,000 people a day. Deep in a corner, to the west of the platform for the shuttle that runs between Times Square and Grand Central Station, Cunningham points out what may be the best place to see the original 1904 line. The shuttle still runs on the trackbed that was part of the first chunk of New York City's subway. It begins after a deep, slowing curve that today's engineers would never allow as it heads from the West Side to the East Side.

Just to the north of the shuttle track is a closed entrance to the Knickerbocker Hotel ("Fifth Avenue Service at Broadway Prices!" was their motto), its name still in rusty, faded brass above the door in full public view. At that point you are also standing in the sub-basement of the old New York Times building, the one now cloaked in the news "zipper." The Times also used to have direct access to the station, and pressmen would load the day's editions onto subway cars for distribution.

Farther south at Astor Place station, also part of the original line, a former entrance to a Wanamaker's department store now leads to a Kmart.

Change.

Still, much remains of the old. Note the beaver on the tile marking Astor Place station in homage to John Jacob Astor's fur trading wealth, or the eagles on the tiles at the stations at 33rd and 14th streets noting nearby armories. At Bowling Green, the end of the tour and the tip of Manhattan, lies one of the system's two remaining dead houses, freestanding buildings covering subway entrances. The other is in the median of Broadway at 72nd Street on the West Side. Sheathed in glass block and floored with stone, these buildings take up just too much valuable space in the crowded city. So, most are gone.

"In this system, nothing ever stays original for long," says Cunningham. "It's always changing."

David Jackson is an editor and analyst at the Brookings Institution.

New York City is celebrating the centennial of its subway with a host of events, exhibits and tours -- where the mode of transportation is the subway.The Manhattan skyline peeks out from the 100-year-old subway line.Signs from retired Red Bird subway cars offer a look at New York's past.