Does tourism leave any heart in San Francisco?

Inside the dark and rusted hulk of Pier 33, it's hard to imagine how this could be an object of contention and desire. With its timbers stripped by age, and its glass streaked to a weather-worn patina, the long, low shed seems a relic from another time – scented by the inescapable smell of fish.

But that, perhaps, is the point. To the fishmongers here, who buy the daily catch fresh from local boats, this is home, and the city's new push to make them move means more than moving vans and a new address. It is a struggle to hold on to one of the last vestiges of the blue-collar San Francisco that has been brought to the edge of extinction by tourism and tea bars.

During the past 40 years, few American cities have seen their characters change more than San Francisco, though its transformation holds lessons for every metropolis.

This was once a town of stevedores and typesetters, dirt-poor poets and rubber-booted fishermen, attracted by the low rents and the wide shoulders of the sea. Today, however, the story of San Francisco would more likely be found in a Nob Hill bistro or the Museum of Modern Art. With the median home price well above $450,000, it is not a city for the faint-of-wallet.

To some degree, this parable is playing out from New York's Times Square to the fish markets of Seattle. To revitalize blighted neighborhoods, cities are looking to attract young professionals and empty-nesters who are lured to the culture and lifestyle of urban centers.But San Francisco, bejeweled by haute cuisine and some of the most breathtaking urban scenery on earth, has become the exampletaken to its extreme.

Now, with the working class that once defined the city largely gone, some are concerned that another part of the city's soul and substance is disappearing, as well.

"[Shipping and industry] brought a cultural tone to San Francisco that doesn't exist anymore," says Stephen Canright of the San Francisco Maritime National Historic Park. "The city kind of grew back from the waterfront."

Today, much of that part of the city's heritage has been erased. Pier 31 has become a giant garage for the faux-cable-car buses that ferry tourists unwilling to wait in line for the real thing. Nearby, horses are being groomed for the carriage rides that begin at Pier 41. Even at Pier 33, the façade has been turned into a restaurant that serves pomegranate molasses glazed liberty duck breast for $29.

Inside the vaulted warehouse, no longshoremen stir. No forklifts lift banana crates from South America or canned goods from South Boston – as was common on the piers through the early 1960s. Even the fishing operations that replaced them are gone.

"It used to be different," says Edward Schach of Quality Seafood as he boxes white filets of sand sole at his Pier 33 dock, several hundred feet away. "Seafood companies used to be all along here."

Within a few years, there might not be any. The city would like to consolidate all the fish processors at a new facility near Fisherman's Wharf. Yet Mr. Schach and others say they have no desire to leave the facilities they've built up over years for another that could be too cramped and glutted by tourist traffic.

It's another example of the maritime industry's waning influence, he says, and it might force more processors out of San Francisco and across the bay.

In recent decades, that has been a trend. To some, the exodus of San Francisco's working class all began with the rise in the 1960s of containerized shipping: San Francisco was unwilling to bring in the massive equipment needed to service such ships, but Oakland was willing.

Since then, Oakland has become the Bay Area's blue-collar, maritime hub, and San Francisco has turned to tourism as its No. 1 industry.

Others, however, point to the '60s era itself as a seminal event. From the beatnikpoets to Ken Kesey and the Grateful Dead, much of what the '60s were began in San Francisco. Almost instantly, the city – which had always had a reputation as a bohemian locale – became a national symbol of independence, free-thinking, and youth.

"The '60s transformed San Francisco more than any other city in the country," says demographer Joel Kotkin.

Indeed, from the late 1960s on, San Francisco's path was set on its current trajectory. To this day, the largest segment of the population here is people age 25 to 44, and the city remains – in some aspects – a sort of 20-something watering hole. Longtime residents are often seen as those who came before the Internet boom and who think parenthood means owning a dog.

Yet even as San Francisco has become increasingly defined byits art exhibitions and tapas bars, some suggest that these trends are mere echoes of the city that sprouted a cultural revolution. For one, none of the bohemians who lived in San Francisco in the 1960s probably could have afforded to live here now.

Some here wonder whether San Francisco has lost some of the depth that resonated with the rest of America in the past, as higher rents and home prices prevent a whole swath of society from taking part.

"It's a terrible city for a 20-year-old poet," says Rebecca Solnit, author of "Hollow City," a book about San Francisco's transformation. "[In the past, San Francisco] felt like a hatching-ground for major movements that were going to sweep over the world. [Now,] San Francisco is just not generating that kind of activity."