Thirty years ago, from May to November, the Louisiana World Exposition gave the globe an insight into New Orleans — and practiced the peculiar arithmetic of our state, as the fair was generally an aesthetic success and a financial failure.

Part of that was a matter of timing, as Louisiana’s economy was in a freefall of oil prices that had long-lasting effects in the 1980s. So the World’s Fair was probably never going to meet the green-eyeshade standard financially.

But it should be properly commemorated, because it was a turning point for Louisiana and New Orleans, and its benefits have accrued since then.

The fair was the brainchild of Ed Stagg, longtime head of the Council for a Better Louisiana. The fair ran during the administration of Mayor Ernest “Dutch” Morial, for whom the convention center — then the Great Hall of the fair — is now named. The fair was supported with private contributions and state funds under outgoing Gov. David C. Treen. It closed in the third administration of Gov. Edwin W. Edwards, having achieved bankruptcy. Of the three politicians, only the latter lived to see the full impact of the money invested in the fair during Treen’s administration.

A historical marker will be unveiled Friday at the corner of Convention Center Boulevard and Julia Street, the heart of the 82-acre fair site. That commemoration is appropriate in part because it holds the motto of the fair: “The World of Rivers: Fresh Water as a Source of Life.”

While few probably remember that, the importance of the Mississippi River to our state and nation has only grown in these three decades, as have the challenges of responding to the Mississippi Delta’s hydrologic, economic and social impacts.

Yet the fair contributed to the economic resources of the region in part because the expensive redevelopment of the old warehouse district — and we mean very old warehouses, in many cases — spurred a real estate revival for the area in the heart of New Orleans.

Today, it is an economic boon for the state and the city. International conventions and meetings of all sorts are drawn to New Orleans, and the development and expansions of the convention center provide a huge economic boost. In 1984, the world was on the cusp of the boom in airline travel that would be a feature of our lives since, but also of vital importance to international tourism. New Orleans and Louisiana had pretty good timing on their World’s Fair, after all.

The sales and property taxes flowing from restaurants and new condominiums and renovated old buildings, in what is now a capital-W Warehouse District, are an obvious benefit to the city of New Orleans. Yet the criticism of the World’s Fair dominated the news about this time 30 years ago.

Redevelopment came slowly to the area, in part because of Louisiana’s recession of the 1980s, but the process was inexorable. Today, what was a shabby and desolate area is now part of a remarkable renaissance of the city of New Orleans.

One of the lessons of that long-ago event is that redevelopment of urban areas is a long-term proposition, one that involves investment in the here-and-now and then, quite often, a long wait for the payback. That wait is usually longer than the four-year term of politicians. With all the contemporary criticism, should we not now declare the 1984 World’s Fair a success?