They met on August 13, 1981, as the sun had just started to hide behind the Hudson River, according to Wilder's detailed account in his 2006 memoir "Kiss Me Like a Stranger: My Search for Love and Art."
Wilder was dressed in a tuxedo. He had just finished shooting a scene on the set of "Hanky Panky," in which he was set to star with Radner.
Their location for the evening was "where the the ocean liners docked on the East River," he wrote. Scenic no doubt.
He walked over to introduce himself to Radner, who he knew from her work on "Saturday Night Live," but not personally.
What happened next was a point of disagreement between the two in the years that followed.
"Gilda said that I rubbed my crotch against her knee when I asked her if I could bring her some tea or coffee," he wrote in his book. "When she told me this story, I said, 'You're nuts!' And she said, 'No, they were your nuts.'"
"Well...it was a beginning."
Radner later wrote of this meeting in her own book: "My heart fluttered -- I was hooked. It felt like my life went from black and white to Technicolor."
It took two weeks for Radner to make a move on Wilder. When it finally happened, she threw him on his hotel room bed and, according to Wilder, said "I have a plan for fun." He rejected her advance.
Radner was married to guitarist G.E. Smith at the time, but she told Wilder that she was unhappy.
"I knew I was going to fall in love with you and leave my husband," Wilder quotes her as saying the morning after he sent her home in a cab.
Wilder was baffled and overwhelmed.
"Gilda, you're talking like this is a fairy tale, and you're going to meet Prince Charming, and everything's going to be all right, and we'll both live happily ever after," he told her, according to his book.
Her reply? "So what's wrong with that?"
It wasn't happily ever after from that moment on. They separated after a year of living together because Wilder felt smothered by Radner's need for his attention. Her struggle with bulimia also put strain on their relationship.
"I thought she was a baby. She couldn't be without me, do without me," Wilder told Larry King in 2002.
But they found their way back to one another and eventually married in 1984, in part thanks to a Yorkshire Terrier named Sparkle, some rat poison and a phone call that alleviated some of Wilder's biggest fears.
When Radner had to miss a planned flight and vacation with Wilder to care for the dog she'd bought during one of their breakups, she told him to go without her. That she'd be "fine."
"That's what I was waiting for for 2½ years," he told King.
Radner and Wilder were married for about two years when she was diagnosed with Stage 4 ovarian cancer.
Wilder remained hopeful until about three weeks before she died.
"I said ... 'I'll exchange life spans with you,'" he told King. "The irony is that I meant it. I thought that she'd pull through and that she would live longer than I would."
Radner died May 20, 1989.
On mourning Radner, in a 2005 interview with CNN, Wilder said honoring their happiness meant living his life.
"If you asked Gilda, she'd say, don't be a jerk. You know, go out, have fun. Wake up and smell the coffee," Wilder said. "Would I want to erase the memories I have, the good memories? No, of course not. But I wouldn't want to mourn for the rest of my life."
Wilder married his fourth wife Karen in 1991 at the Connecticut home Radner left him.
Sparkle was in attendance.