MIAMI — Florida was built on the seductive delusion that a swamp is a fine place for paradise.

The state’s allure — peddled first by visionaries and hucksters, most famously in the Great Florida Land Boom of the 1920s — is no less potent today.

Only, now there is a twist: Florida is no longer the swampy backwater it once was. It is the nation’s third most populous state, with 21 million people, jutting out precariously into the heart of hurricane alley, amid rising seas, at a time when warming waters have the potential to bring ever stronger storms. And compared with the 1920s, when soggy land was sold by mail, the risks of building here are far better known today. Yet newcomers still flock in and buildings still rise, with everyone seemingly content to double down on a dubious hand.

Florida mostly survived Hurricane Irma, which delivered its most severe damage elsewhere. More than a week later, nearly 400,000 weary, sweat-soaked people in the state remain without power; at least 50 did not survive the storm or its even more dangerous aftermath; and the billions in property damage are still being calculated. Meanwhile, Hurricane Maria rumbles across the Caribbean.

Many saw last week’s storm as another dress rehearsal for the Big One. But it wasn’t much of a reckoning for a state mostly uninterested in wrestling with the latest round of runaway development, environmental degradation and the mounting difficulties from catastrophic storms. Since the recession’s end, new condominiums and houses have been built at a gallop. Many rise on or near the coast, or, in some cases, environmentally important wetlands, which were nature’s way of absorbing water. Meanwhile, the seas climb higher, floodwaters roam wider, evacuations grow increasingly tangled, the cost of insurance jumps and infrastructure decays.