WASHINGTON (CNN) -- It's not the Bill of Rights. It's not the Declaration of Independence. It's not even the Constitution. No, the most requested item at the National Archives is a photograph of Elvis Presley shaking hands with President Nixon during a visit to the White House.
"It's very popular," said Laura Diachenko, a spokeswoman for the government agency, which stores and displays millions of historical documents, pictures, videos and artifacts. And the interest has increased this week with the 25th anniversary of Presley's death.
The picture is the result of an unannounced December 21,1970 visit that Presley paid to the White House. Wearing a dark cape, jewelry, an open-collared shirt and a large, garish belt buckle, Presley -- 35 at the time -- wanted to visit the president to request becoming a "federal agent at large."
Presley explained his goal in a six-page letter to Nixon.
"I have done an in-depth study of drug abuse and Communist brainwashing techniques, and I am right in the middle of the whole thing where I can and will do the most good," Presley wrote in part, citing his status as an entertainer. "I am glad to help just so long as it is kept very private."
Presley asked Nixon for "federal credentials" and expressed his concern with some current developments in the country.
"The drug culture, the hippie elements, the SDS, Black Panthers, etc. do not consider me as their enemy or as, they call it, the establishment," Presley wrote. "I call it American and I love it. Sir, I can and will be of any service that I can to help the country out."
Jeff Donfeld, a White House aide at the time, recalled that December morning when Presley showed up at the White House. A colleague called and announced, "The king is at the gate. I said, 'What are you talking about?' He said, 'The king is at the gate.' "
Donfeld was stumped. "I didn't have a clue," he recalled in an interview with CNN's Gary Tuchman. "He said, 'Elvis Presley.' I said, "You've got to be kidding me.' "
Presley arrived with bodyguards and an unusual gift for the president: a World War II commemorative Colt 45 pistol with seven silver bullets. "The Secret Service, of course, took those away," Donfeld said.
Presley's visit with Nixon prompted a flurry of memos at the White House. When Presley arrived at the White House gate, Nixon aide Dwight Chapin sent a missive to H.R. Haldeman, Nixon's chief of staff: "He would just like to say hello and present the president with a gift."
Chapin told Haldeman he though it would be good for Nixon to meet Presley because the entertainer was "very pro" Nixon.
"In addition, if the president wants to meet with some bright young people outside of the government, Presley might be a perfect one to start with," he wrote. That prompted a retort, apparently from Haldeman. The words, "You must be kidding" are scribbled on the margin of the memo.
Nixon's staff armed the president with talking points, focusing on drug abuse, before the meeting took place. They included one suggestion the president would pass along to Presley: "Record an album with the theme 'get high on life' at the federal narcotic rehabilitation and research facility at Lexington, Kentucky."
That album was never recorded.
Presley, however, did get a "specially prepared" badge from the Bureau of Narcotic and Dangerous Drugs.
And he found a friend in Nixon, who sent the singer a note after the visit thanking him for his "impressive gift."
At the Nixon presidential library in Yorba Linda, California, Elvis-meets-Nixon items are hot sellers, said Arianna Barrios, the library spokeswoman. The items include pens, soap and shot glasses.
She said it's easy to understand the fascination with the meeting. "They were from very different worlds," Barrios said. "But they were at the time the two most influential people -- one in politics and one in music."
One more thing: Los Angeles Magazine named an Elvis-meets-Nixon cotton throw blanket as the city's best souvenir this summer. It beat out the LA County Coroner's Office chalk-body-outline beach towel for the honor.