At the same time, Las Vegas suffers the pitfalls of being a one-industry town. Baked into its economy are minimal taxes and a state government inclined to ship much of what Las Vegas contributes to the rest of Nevada, which, among other consequences, insures the school system is perennially poor. Casino moguls, needing a steady supply of parking attendants, hotel maids and blackjack dealers, not college-educated workers, were once fine with that. But times are changing. Now the lack of good public schools and downtown amenities — demanded by those mobile and educated young Americans other cities are competing to attract — has become a liability.

On top of which, Las Vegans I spoke with, young and old, complained about not having “enough authentic places,” which are “locally owned, one of a kind, less corporate,” as Tyler Jones, a 35-year-old architect-developer of luxury homes and third-generation Las Vegan, put it to me. They wanted a Las Vegas for Las Vegans.

Which is where Tony Hsieh comes in.

Downtown began to decline by the 1960s. The casinos, department stores and middle-class homeowners fled south to the Strip, seizing upon cheap and plentiful land. During the 1990s, the Fremont Experience turned five desperate blocks of what used to be the heart of the downtown gambling scene into a pedestrian concourse beneath a lighted canopy that pulled in low-end tourists but few jobs or residents. It’s now a blighted attraction. Neonopolis arrived in 2002, a retail and entertainment mall, which soon went belly up, leaving a fortress-size hole amid the pawn shops and homeless shelters.

Since then, there has been progress. The Cleveland Clinic Lou Ruvo Center for Brain Health, designed by Frank Gehry, opened downtown in 2010; the popular Smith Center for the Performing Arts, a $485 million project, last year; along with a new City Hall. And back in 2007, a small bohemian speakeasy called the Downtown Cocktail Room opened on the corner of Fremont and Las Vegas Boulevard, once the main intersection. Hanging out in the Cocktail Room a few years ago, Mr. Hsieh began to picture a different vision for the neighborhood: as an affordable locus for upscale young adults, having little or nothing to do with gambling.

In some ways, the most fascinating aspect of this vision is the relocation of Zappos. Moving its headquarters downtown represents a pointed alternative to the multibillion-dollar suburban office parks that Google and Apple are building in Silicon Valley, notwithstanding that so many of their own employees want to live in, and commute from, San Francisco. Mr. Hsieh has bought into the solid notion that chance encounters on the street or at a club — urban collisions — spark innovation: cities, inherently, nurture the economy and culture.

It’s a gentrifying idea that comes at the cost of displacing some existing businesses whose owners say downtown Las Vegas wasn’t a blank slate. Critics like Joel Kotkin, a fellow of Urban Futures at Chapman University, have told The Las Vegas Review-Journal that Mr. Hsieh’s project commits tax dollars (by, for instance, helping finance Zappos’s purchase of the old City Hall) that might otherwise be spent on training programs or buses.