The corridor of power at the Smithsonian Institution in Washington is lined with framed portraits of its past leaders – a succession of white men of a certain age. But change is coming to the biggest museum, education and research complex in the world.

On Tuesday, the Smithsonian named Lonnie Bunch as its 14th secretary – and the first African American to hold the position in its 173-year history.

Bunch, 66, will step up from his current position as founding director of the institution’s National Museum of African American History and Culture. The significance of his appointment is impossible to miss, especially for a body with several art galleries and museums that neighbor the White House and US Congress.

“In some ways, my career in museums has been about kicking down doors and breaking ceilings, whether it’s as a curator or as a museum director,” Bunch told the Guardian in the Smithsonian “Castle” on the national mall. “I know I was hired because I have a lot of skills but I also understand the symbolic value of being the first African American, that there are still doors people can’t get in.

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“What you realise is that the Smithsonian is bigger than a museum complex so that it will have a ripple in many other ways. That is something that humbles me but it’s something that I think is important.”

The Smithsonian has been attempting to change to better reflect America. During the four-year tenure of the current secretary, David Skorton, two in three recruits at director level or higher were women or people of color. Last year, Ellen Stofan, former chief scientist at Nasa, became the first female director of the popular National Air and Space Museum. Bunch, who has written extensively about diversity in museum management, wants to continue the trend.

“I just think that you’re a better institution when you have a diversity of people telling you the stories you want to explore,” he said.

“My hope is that the Smithsonian has made important strides in that area and I will keep pushing that, because I do think that if we are the place where not just America but the world comes to see what it means to be an American, then I should be able to walk into every institution, every museum, every shop and see that diversity of America.”

Facebook Twitter Pinterest Bunch stands in front of one of the engraved walls of the Smithsonian’s National Museum of African American History and Culture in Washington in 2016. Photograph: Paul Holston/AP

That ambition is also likely to be reflected in the content and collections.

“ In essence, what I want to see are exhibitions that revel in specificity, ethnicity, race but claim their Americanness. You’re not just telling the story of the Irish in London; you’re telling the story of London but you’re looking at it through the eyes of the Irish community. So that’s the kind of thing that I’d like to see us do more of.”

Born and raised in Newark, New Jersey, Bunch is the first historian to be elected secretary. He has written on topics ranging from the black military experience to the American presidency to the impact of race in the American west. He has also spent more than 35 years in the museum field, including 29 at the Smithsonian.

Bunch also had a year based in the UK, teaching at University College London and working on a book. “The goal was to teach at night and write all day and then find time to root for Arsenal and go to the theatre every weekend.”

When Bunch became director of the National Museum of African American History and Culture in 2005, he had one staff member, no collections, no funding and no location. He rallied donors of every level and worked with Congress to fund the museum through a public-private collaboration. In September 2016, the museum opened on the national mall and was widely hailed as an architectural masterpiece. It has welcomed about 4 million visitors and built a collection of 40,000 objects.

Like baseball, the Smithsonian could be said to offer some non-partisan glue to help hold a divided country together. Artsy liberals rub shoulders with tourists wearing “Make America great again” hats and sweaters at some of its main attractions. The opening ceremony for the African American museum featured the former Republican president George W Bush and his Democratic successor, Barack Obama.

Bunch reflected: “I think that there are always moments in America where you have these tensions, where there are battles over what does it mean to be an American, what is America’s identity. My goal is to help people transcend partisanism, to try to bring people together around history, culture and science.”

Donald Trump, not a noted student of history, visited the African American museum just a month after taking office and went on a brisk tour. Bunch said diplomatically: “I am a museum director and a historian and my belief is that my job is to educate everyone. I was pleased when President Trump came into the museum because there were stories that I didn’t think that he knew but he now began to engage.

“For me, that’s the joy of the Smithsonian. There are people who may not care about natural history or may not care about the arts but when they do the Smithsonian, they’ll wrestle with those questions, and so you have a chance to be the great educator. I think that’s what we did with anybody that came in our doors.”

Many in Washington, a Democratic stronghold, are gripped by despair at the Trump presidency, which they accuse of enflaming divisions and emboldening racists. Bunch, however, takes a historian’s long view. “When you look at the history of race in America, the people who were lost, the violence, the failed, crushed hopes as a story, you have to be optimistic because you realize that people continue to struggle to demand America live up to its stated ideals.”

Founded in 1846 with a bequest from the British scientist James Smithson, the Smithsonian boasts 19 museums, the National Zoo and nine research centres. Bunch – charged with raising more than $500m in private donations per year to supplement its $1bn government subsidy – will take over on 16 June from Skorton, a cardiologist, who will become president and chief executive of the Association of American Medical Colleges.

Skorton said on Tuesday: “I think diversity in general could not be more important in the world right now. After all, aren’t we having a hard time everywhere listening to each other and talking with each other because of our differences? They may not be ethnic differences; they may be political differences, they may be gender differences. We’re having trouble reaching across that chasm and so I think diversity is incredibly important.”