A Guinness World Records representative said the effort drew more than 2,000 people. At least 5,000 were needed for an official record, said Guinness adjudicator Philip Robertson.
The Beatles' 50 Biggest Billboard Hits
That did not quell the spirit of the warm, sunny day that brought together everyone from aging hippies to schoolchildren not yet born when Lennon died.
He was fatally shot in 1980 at his apartment building on Manhattan's west side just across from Central Park.
More than three decades after her husband's assassination, Lennon's 82-year-old widow summed up Tuesday's event using his famed lyrics, "Imagine all the people living life in peace... ."
She concluded: "This is the best present to John."
In 2009, 5,814 people formed a peace sign in Ithaca, New York. But it was not clear whether participants stood in place in the shape of the symbol for at least five minutes, as required, and therefore no official record was set, Robertson said.
Ayeisha Bradley and her 9-year-old son, Salahedin Callier, were not there to compete.
Beatles Timeline: The Fab Four's 50 Most Memorable Moments
The Manhattan mother and her son, both Muslims, kneeled quietly under a tree, praying.
"To me, peace is something that should stop fighting, you need peace like, as in, if somebody is fighting with you and they act like they're not your friend - act like you're their friend," the boy said. "That's making peace. If there's not a solution, then you're part of the problem."
His mother added, "Before we make peace outside ourselves, we have to make peace within ourselves."