WASHINGTON - When Barack Obama steps off Air Force One in South Dakota on Friday, he will join an exclusive group of US presidents who have visited all 50 US states while in office.

Jimmy Carter, Ronald Reagan and George W. Bush didn’t do it. After 49 states, Bush did not fancy a trip to liberal Vermont during the financial crisis. But Bill Clinton did and George Bush senior managed it in just one term. US presidencies are made and measured by big speeches and grand symbolic gestures, but also figures and statistics. How many times has the president vetoed a bill from Congress? How many executive orders were issued? How many state dinners were hosted at the White House? And how many states did he visit?

‘Visiting all 50 States is an important goal,’ said Brendan Doherty of the politics department at the United States Naval Academy. ‘State identity matters so much in the American system: Presidential elections are held by States, there are equal State representations in the Senate.’ ‘Even if they have already visited states where over 99 percent of the American population live, they want to make a visit to each state simply so that they can say that they have.’ Obama took to local channel KSFY-TV to announce the trip, which will include a commencement address at the Lake Area Technical Institute. ‘May 8th we’re coming,’ he said. ‘I can’t let my South Dakota friends feel neglected.’ South Dakota Secretary of Tourism James Hagen, who invited Obama to visit as far back as 2013, said ‘I am absolutely convinced he is saving the best for last.’

It might be surprising that such a history-minded president would wait so long to visit the state that is home to Mount Rushmore - a rock face emblazoned with the likenesses of George Washington, Thomas Jefferson, Theodore Roosevelt and Abraham Lincoln.

But even in his election drubbings of Republicans John McCain in 2008 and Mitt Romney in 2012, Obama was roundly defeated in the state. With a solidly Republican voter base, South Dakota is far from Washington, with a population of less than a million and with only three of 538 electoral votes up for grabs at the presidential elections. It was never going to be top of Obama’s travel list. But with no more elections to run, Obama may as well make a visit.