Sometimes I think there are two types of Philadelphians: those who think everything we do will go wrong, and those who are sure it will.

That's why we're sometimes called Negadelphia. How we handle big events is kind of a civic Rorschach test.

But there is evidence that we don't screw up everything we touch.

So far this century, we hosted: the Republican National Convention in 2000; a World Series victory parade in 2008; Pope Francis' visit in 2015; the Democratic National Convention last year; various summer festivals, and this week the NFL Draft.

Looking back to earlier centuries, however, yields mixed results.

The United States' birth certificate was written here in 1776, and the 1876 Centennial celebration in Fairmount Park introduced the United States' industrial ingenuity to the world. It attracted 10 million visitors to a country with 40 million residents.

"Reporters with a high level of skepticism and cynicism came to the fair, and what they saw blew their socks off," says Sam Katz,  historian, documentarian, civic leader, and public intellectual. "Who knew little America was the leading industrial country in the world?"

After the Centennial, everyone knew.

The telephone, typewriter, sewing machine, and monorail were among the American inventions introduced at the Centennial. Also Heinz ketchup, no kidding. The planning started nine years before the May 1876 start of the exposition, the first World's Fair held in America.

One century later, the Bicentennial in Philadelphia fizzled. Most of the blame was laid at the feet of Mayor Frank Rizzo, who had asked for federal troops to handle anticelebration protesters, but the truth is more complicated. This was one year after the United States suffered a humiliating defeat in Vietnam, and the '70s were often as chaotic as most of the '60s. Not to mention Legionnaires' disease. Potential visitors had lots of reasons to stay away.

Planning for the Bicentennial began 10 years out. After years of infighting between Boston and Philadelphia, the American Revolutionary Bicentennial Commission chickened out and chose no city to be the focus.

In between the Centennial and the Bicentennial was the failed 1926 Sesquicentennial.

In eight years it will be 2026 — the Semiquincentennial, our nation's 250th birthday celebration, which Philadelphia wants to grab for its own.

Hey, even the Sesquicentennial wasn't as bad as people think, says Andrew Hohns, adding that each of these celebrations added something of value to Philadelphia.

Hohns, 38, who manages an infrastructure fund, is a Posidelphia kind of guy who sees the glass as half-full.

I have to call him a visionary, because he started thinking about 2026 back in 2008, when the rest of us were thinking about the World Series.

Hohns brushes off any suggestion that this was his idea, but he surely was one of the people who put the celebration on our radar. Not surprisingly, he was named chairman of the board of USA250, the nonprofit umbrella group charged with organizing the celebration.

"We were already too late," he says. "The Chinese have a proverb that the best time to plant a tree is 20 years ago and the second-best time is today."

Plans are amorphous at this point, but Hohns says that although it will be a party, "in the true spirit of America we work to earn this party by engaging in incredible self-improvement."

The key theme is drawn from a founding document — life, liberty, and equality.

Rather than a single focus, Hohns imagines "exploring us as people, our many heritages — Polish Americans in Port Richmond, Irish Americans in Pennsport, Italian Americans in Bella Vista, Jamaican Americans along Baltimore Avenue," Hohns says. "Philadelphia is America. Every facet of America, for better or worse, is on display."

The "glue" that will hold the whole shebang together is "the incredible spirit of patriotism and perseverance we have as a people," he says. "Americans are unique in feeling their national identity through individual aspirations."

USA250 at this point has one paid employee, executive director Jon Herrmann. The board is heavy with business types.

You know what it can use? Youse.

You can become a founding supporter of USA250 for as little as $25. Visit www.USA250.org for free, and be the first kid on your block to find out what will be happening in Philly eight years in the future.

When Olivia Nutter is mayor.