David S. Ferriero, who has been the archivist of the United States for more than a decade under three presidents, is planning to retire in April.

Ferriero, 76, has been head of the National Archives and Records Administration since he was appointed by President Barack Obama and confirmed by the Senate in 2009.

“It has been the honor of a lifetime,” Ferriero wrote in a note to his staff Wednesday. “My time here has been filled with opportunities, challenges, and awesome responsibilities. … I am humbled and awestruck and so deeply grateful — grateful to all of you.”

In addition to housing national treasures such as the Declaration of Independence, the Constitution and the Bill of Rights, the National Archives holds 13 billion pages of text, 10 million maps, charts and drawings, as well as tens of millions of photographs, films and other records.

The archives is also responsible for the nation’s 13 brick-and-mortar presidential libraries.

Before coming to the agency, Ferriero was director of the New York Public Libraries and served in top positions at the libraries of the Massachusetts Institution of Technology and Duke University. A native of Beverly, Mass., he served as a Navy hospital corpsman during the Vietnam War.

A self-described introvert, he is reserved and has a dry sense of humor. On his watch in 2014, the National Archives held its first sleepover.

He has pushed the digitization of the archives, and he embraced social media. In November, he noted in a blog post, “We know that not everyone can come to our facilities [for research] and providing these records online democratizes access.”

He has also promoted the role of “citizen archivists” who volunteer to transcribe and review historic documents online.

“I have met or known half of all Archivists of the United States … and none has done better” than Ferriero, historian Michael Beschloss tweeted.

One of the items framed in Ferriero’s office is a copy of a letter he wrote to President John F. Kennedy when he was in high school. The letter had been found at the Kennedy Presidential Library in Boston.

The future archivist asked about the Peace Corps and requested a photo of JFK.

Later, the Dwight D. Eisenhower Presidential Library found two letters Ferriero had written to President Eisenhower as a youngster, and the Lyndon B. Johnson Presidential Library found one he had written to President Johnson. Ferriero had them framed in his office, too.

In 2020, the National Archives faced criticism when it posted in its headquarters building an exhibit with a picture that had been altered to blur out words suggesting criticism of President Donald Trump.

The large color photograph, designed to celebrate the centennial of women’s suffrage, showed a massive protest crowd on Pennsylvania Avenue during the Women’s March on Jan. 21, 2017, the day after Trump’s inauguration. The original photo had been altered to obscure some words on signs held by marchers.

A placard that proclaimed “God Hates Trump” had “Trump” blotted out so that it read “God Hates.” A sign that read “Trump & GOP — Hands Off Women” had the word “Trump” blurred out.

Less than 24 hours after Washington Post reporter Joe Heim pointed out the alterations, the National Archives apologized.

“We made a mistake,” it said in a statement. “As the National Archives of the United States, we are and have always been completely committed to preserving our archival holdings, without alteration.”

“We were wrong to alter the image,” it said. “We apologize, and will immediately start a thorough review of our exhibit policies and procedures so that this does not happen again.”

The altered picture was removed and replaced with an unaltered one.

“Our credibility, so important to our mission, understandably has been questioned,” Ferriero wrote on his blog. “I take full responsibility for this decision and the broader concerns it has raised …[and] pledge to restore public confidence in this great institution.”

The National Archives is headquartered in a massive 84-year-old granite and limestone landmark on Pennsylvania Avenue in Washington’s Federal Triangle. A “temple to American history,” Ferriero called it.

The agency also has a large, more modern complex in College Park, Md.

Deputy Archivist Debra Steidel Wall will serve as acting archivist until the president nominates and the Senate confirms a successor.

“It is not easy to leave you with our important work continuing, especially initiatives to foster equity and enhance the employee and customer experiences,” Ferriero told his staff. “However, our profession is one of stewardship, where despite our enduring responsibilities, we are here for what amounts to a brief period of time.”