By Kevin Deutsch

Just in time for the 20th anniversary of its creation, the No. 9 train is back in service. At least, two signs for it are.

Four years after the line was banished from existence, veteran straphangers and subway novices alike have been puzzled by the re-appearance of the No. 9 sign at the entrance to the 242nd Street Station. Two stops away, at West 231st Street, a small yellow sign hanging above the track — emblazoned with the numbers 1 and 9 — also lends credence to the possibility that two trains still make the 14.7 mile trek from South Ferry to Van Cortlandt Park.

“Do you know which one of these trains goes to downtown Manhattan?” an apparent subway newcomer asked one recent afternoon, gesturing toward the No. 9 and No. 1 signs at the 242nd Street Station.

The signs, and the questions they spurred, are a reminder of the No. 9 train’s brief but memorable life. Twenty years ago this month, the train commenced its journey through the subway system, bringing “skip-stop” service to the No. 1 line. It was an express route, bypassing certain stations serviced by the No. 1 Broadway local.

By 2005, though, the No. 9 had outlived its usefulness. The stations it skipped were used more and more, so bypassing them made little sense. The line was shut down and mostly forgotten, just another piece of disposable transit history.

All traces of the No. 9 train — from its red emblems to its route on subway maps — were supposed to be removed in 2005. More than 900 signs with the No. 9 emblem were covered with vinyl patches at the time, including the one at West 242nd Street.

Then, a few weeks ago, that patch came undone and disappeared. Maybe the summer downpours brought it down. Or perhaps a nostalgic straphanger peeled it off, hoping to resurrect a forgotten piece of the city.

“Did they bring back the nine?” Frank Petrocelli, 56, wondered aloud as he emerged from the station Sunday. “I always liked the 9. Got me here quicker.”

Alas, New York City Transit squashed any dreams of a resurrection.

“I hope they don’t think the nine is coming back,” Deirdre Parker, spokeswoman for the agency, said of local riders. The downed vinyl covering will be reported to station workers, and the No. 9 emblem covered once again, she said. The same goes for the smaller sign at the 231st Street Station.

When told that the re-emergence of the No. 9 sign was simply a fluke, Mr. Petrocelli grew contemplative.

“Everything gets covered over at one time or another around here,” the construction worker said. “It makes it easy to forget the past.”