JFK's Secret Love Letters Sold for $115,537

March 4, 2010— -- John F. Kennedy's secret love letters to Gunilla von Post, a Swedish woman with whom Kennedy had had an affair, were sold for $115,537 Wednesday night, according to Legendary Auctions, which carried out the sale.

After widespread national and international interest, the letters went to an anonymous West Coast collector, according to Julie Stoklosa, a spokesperson for auction house.

The $115,537 price included an 18.5 percent buyer's premium, Stoklosa said.

Three weeks before Kennedy married Jacqueline Bouvier, he met von Post and the two began a fleeting but passionate romance. The relationship continued after Kennedy was married, von Post says.

Kennedy's relationship with the Swedish woman was documented in a series of poignant letters and telegrams. Von Post kept the correspondence locked away, so the letters were never made public until she put them up for auction last month.

In the letters, Kennedy expresses, in his scrawling longhand, his feelings for von Post.

"Under that beautiful, controlled face that still haunts me -- beats a warm heart," Kennedy wrote in a letter dated Dec., 18, 1954, according to a transcript on LegendaryAuctions.com.

The two met on the French Riviera in the summer of 1953. He was 36, and she was 21. They danced all night, and parted with a passionate kiss.

But their plans for a secret rendezvous fell apart when Kennedy badly injured his back.

In November 1954, he wrote to her from the Hospital for Special Surgery in Manhattan. His letter seemed full of longing.

"I am still in the hospital after two months. I was terribly disappointed that at the last moment I was not able to come to Europe, especially when you were going to be in Paris and we could have had such a good time. …" He wrote that he was going to see her without fail if she wasn't "all settled down" by then.

In the same letter, he wrote at the end: "Is there any chance you will be coming to the U.S.?"

Von Post, now 78 years old, first revealed the affair in a 1997 book, "Love, Jack." In an interview that year with ABC News' "20/20," she described how her heart went "boom-boom-boom-boom."

"I was very happy to hear from him, but I said, 'He's a married man,'" she told "20/20."

It wasn't until the following year that the two got together, slipping away to an old castle in Sweden.

"I borrowed him for a week, a beautiful week that no one can take away from me," she told "20/20."