Sometimes a town grows very rapidly, doubling in population or more in a very short time. In The Wild West, this often happened around gold or silver strikes, or where water was discovered in an arid area. While the rapid expansion lasts, the community is a Boom Town.
Boom towns tend to have a lot of new construction, much of it ramshackle, to house the new residents and businesses. In Westerns, most of the businesses will be saloons, gambling halls, and other entertainments designed to get the newfound wealth of the residents into the business owners' pocket. Churches and schools will come later, with the maturation of the town.
Often, the growth of the town will attract undesirable elements, leading to lawlessness and the need for law enforcement to clean it up. Certainly, any boom town is likely to be an Adventure Town.
Since a boom town often relies on a single resource or attraction, if that dries up the town will start dying, quite possibly becoming a Ghost Town.
Note that several works have used the title "Boom Town" to refer to communities about to blow up. Not the same thing.
Not to be confused with short-lived series Boomtown, or the Doctor Who episode.
In The Dandy there was a Molly cartoon where she demanded she have her own award ceremony. So she managed to get a construction company to build a building (for the awards ceremony) by the evening.
Like all Western tropes, it was parodied in Lucky Luke, where the title character was more or less forcibly put into the law-enforcing position. A patch of desert one day becomes a little town the next, with various incidents: a man going to sleep on the ground and waking up to find the place has become an expensive hotel whose owner is urging him to pay; clients waiting impatiently at the bar in a saloon while the walls are being built around them; customers (including a robber) waiting impatiently for the local bank to finish being built and open; and, of course, houses built any old how directly against each other.
Luke: No way, we need to knock down some houses and build streets...
Official: Is that really necessary, Luke? The street is where accidents happen...
In The Adventures of Tintin in America, the discovery of oil in a piece of Injun Country leads to its overnight conversion into a bustling small city (the Indians are forced to leave within an hour).
The page quote comes from an Astérix film, where the eponymous hero and Obelix go to sleep in a haunted plain... and wake up in Rome (something never explained, but as that film's epilogue remembers, "Let's face it, this is only a cartoon film, and anything goes!").
The town in the western spoof Support Your Local Sheriff springs into existence almost overnight after the accidental discovery of a rich gold strike.
Like many small, rural towns dominated by one industry, the coal mining town of Grantville was shrinking and withering during the 1980s and 1990s... until a Negative Space Wedgie transplanted the town to central Germany during the Thirty Years' War. The town suddenly found itself the most high-tech place in the world and its population mushroomed with refugees. Inhabitants have tried to maintain building codes and labor standards for all the new construction and industry, but the fact that they haven't always succeeded has been a plot point more than once.
In the same series, Magdeburg rises from the ashes of a brutal sack of the town (as in Real Life), becoming not only the capital of the new empire headed by Gustavus Adolphus, but also an industrial center in its own right, thanks in part to assistance from uptimers.
In A Town Like Alice, the heroine turns a Ghost Town into a Boom Town with an application of money, enterprise, and motivation.
The obscure Venezuelan novel Oficina Número 1 takes place constrating the Ghost Town in the prequel Casas Muertas.
Tell Sackett founds one of these almost inadvertently in the Louis L'Amour novel Sackett, as a cover for his more profitable gold strike some distance away.
Actually, most of Louis L'amour's novels have a boomtown... in Fallon, the titular character starts a boomtown on top of a boomtown, in The Iron Marshall it's pointed out several times that the town didn't exist just a year before, in Bendigo Shafter, building a town is the whole point... etc. etc.
One of the most extreme examples is Jeuno in Final Fantasy XI. It's certainly longer in the time to grow, but you can't really complain when a small fishing village, in four years, became the economic center of an entire continent and an independent nation.
The most extreme example has to be New Town in Dragon Quest III: If you time it right, you can turn a mostly-vacant patch of land a hundred world-map tiles from nowhere into the game world's largest and most-populous town and witness it undergo a revolution against the leader (whom you appoint). The game has an active day-night cycle, so all of this can transpire, literally, within a few days.
Featured again in Dragon Quest IV. You help a young entrepreneur to develop a boom town in a patch of desert (which previously was a bazaar) by recruiting people from around the world. Completing this sidequest will turn the boom town into a castle. Dragon Quest VII featured this too.
The town of Township (yes, that's its name) from Breath Of Fire 2 starts out as a ruined building that your friend Bow is forced to restore while he hides from the law. When the house gets appropriated by shamans, you hire a proper carpenter to build more buildings, while you recruit helpful people for the population. And it can fly, too. All over the course of one game.
Your castle in Suikoden is usually one of these, as it fills up with the 108 stars and various hangers on. Even if it starts out deserted, by the end of the game your castle is complete with a farm, multiple stores, a blacksmith, a restaurant, an orchestra, an inn, a bathhouse, and any number of other amenities and services.
A game-spanning sidequest in Terranigma involves building up towns from their initial Dark Ages-state into modern societies. In fact, if you don't participate in this activity, it creates plot holes later on.
Container City in Brink is this, a sprawling town built out of shipping containers, built when refugees arrived on The Ark by the boatload. Supposedly modelled on the favelas of Brazil.
Newcastle in Might and Magic IV can be turned from a ruin to the most advanced city on Xeen's Cloudside in a fingersnap, if you have the Megacredits to build it.
The City of Luin becomes this in Tales of Symphonia. Well first it was a decent sized city, got burned down to the ground, and then you help restore it. Give enough money and you have giant statues of Sheena, Lloyd, and Raine.
Constantinople (now Istanbul) sprang up just about overnight when Constantine decided to make it the new capitol of the empire.
Sunomata Castle was built (or at least repaired to full functionality) in one night.
Tombstone was a boom town around the time of Wyatt Earp, which is covered in many movies.
St. Petersburg is arguably a subversion, since it was built over the course of several years; on the other hand, as soon as it became the capital, it was filled with many more people than it could support, including many, many construction workers.
"Residence cities" (i.e. the seats of royal courts) throughout the pre-modern history of most of Asia. There were a lot of those; many of them were founded and abandoned overnight on the ruler's whim (some Indian dynasties preferred to abandon the old capital and move a new one whenever a new ruler arose).
Shenzhen, China is probably the uber example. 30 years ago there was almost nothing there. Not a city, not a town, barely a fishing village. Today it's got 7 million people, is the third largest city in the entire country and, quite possibly, the richest. How you ask? Magic, of course!. The magic of being just on the mainland side of Hong Kong when China decided to open up as well as a pet project of the premier.
The mining towns in the Klondike circa 1899.
They also created a big boom for Seattle
And the ones in California 50 years earlier.
Ireland in the 80s was a million miles away from Ireland of the 00s. A lot the people who moved abroad to find jobs had by now come back, which attracted a lot of property developers. This led to an entire country almost solely based on a housing bubble. Suffice to say, we're not a boom country any more.
Soviet "Monotowns". Basically, a manufacturing plant, factory or mine was built in the middle of nowhere, and then a town was built around it. Resulted in a lot of troubles in The New Russia, with the industries dying out and the towns getting plagued by unemployment, since everybody was supposed to work at a single workplace.
Las Vegas back when the mob first came in and started building the hotels and casinos the city is now famous for.