On Feb. 7, 1964, thousands of screaming fans greeted John, Paul, George and Ringo as they stepped off of their Pan Am flight at Kennedy Airport.

The Beatles' first New York trip introduced the Fab Four to enthusiastic U.S. audiences, heralding their enormous impact on western culture, which has ranged from music to fashion to hairstyles, according to Bruce Spizer, the author of eight books about the group, including "The Beatles are Coming!: The Birth of Beatlemania in America."

Before The Beatles, no British musical act had ever had long-standing success in the United States, Spizer said.

But the group's Feb. 9 performance on "The Ed Sullivan Show" garnered 73 million viewers, making television history.

"You didn't have YouTube, you didn't have DVDs or Blu-Ray -- not even Beta Tapes or VHS," Spizer said. "Before this there was no way to see The Beatles perform."

During that same trip, The Beatles took the stage at Carnegie Hall twice in the same day. Later in the year they played two nights at the Forest Hills Tennis Stadium in Queens, the former site of the U.S. Open. The following year they played to an audience of 55,000 people at Shea Stadium, a landmark event that was the first rock concert of its size, according to Spizer.

On their first U.S. trip, the Beatles stayed at the Plaza Hotel, which is among the sites to which native New Yorker Susan Ryan takes die-hard Beatles fans when she leads them on her Fab 4 NYC Walking Tour around Manhattan.

Other sites on the tour include the Ed Sullivan Theater, now home to "The Late Show with David Letterman," Tavern on the Green, where John Lennon celebrated several of his birthdays, and The Dakota, where Lennon lived with Yoko Ono until he was fatally shot while entering the building in 1980.

Ryan's personal favorite Beatles spot is Strawberry Fields, a memorial created in Central Park to honor Lennon after his death.

"We New Yorkers loved having him here," she said about Lennon's time in the Big Apple. "I can't tell you of any New York Beatles fans who weren't proud of that."

Ryan said The Beatles had strong personal connections to the city. "They had these ties and a huge impact that makes them part of our city," Ryan said. "They've adopted us as much as we've adopted them," she said.