Early on when developing New Shoregate, we agreed on certain core-aspects the new sim should represent. There wasn't actually much time we spent on debating these points, they just fit together simply. One thing was that we wanted a Steampunk sim, then it was supposed to become more dark and "gothic" than its predecessor, of course we wanted zombies too, and a certain amount of weirdness. Well, I think we got that pretty fine!
The backstory did also happen like by itself. There had to be a cause for the zombie invasion after all, and what fits better to Steampunk than good ol' H.P. Lovecraft? To write a first version down wasn't much a stretch then. Like the city itself the story was already there - it just needed to be put on "paper". It is quite possible that the Backstory gets extended or - in details - changed in future, where necessary - you can see this as the first version of the story of New Shoregate:
"New Shoregate was once a prospering seaport at England's coast, until that stormy and unholy night of the 17th November 1898. It was the night when the Airship HMS Arkham crash-landed near the lighthouse when returning from its expedition to the South-Pole.
The citizens of New Shoregate were curiously awaiting the return of the ship: Before departing to New Shoregate, the leader of the expedition telegraphed to have uncovered mysterious artifacts from an ancient civilization, which „represent a revolution in archeology and paleontology and will put the evolution of man in a completely new context“.
But neither the crew of the Arkham, nor the citizens of New Shoregate ever got the chance to celebrate the return of the expedition. Witnesses later reported the wind that night howled like a furious beast and dragged the vessel to the ground like by a giant invisible claw.
No-one of the locals, who hurried to the wreck to rescue the crew, ever in their lives talked about the things they found and what exactly happened there, but soon the flames of a large fire at the site of the crash-landing were visible from everywhere in the city. The reasons for this fire could never been found out and many of the rescuer died in the months after that cursed night.
People soon began to speculate that the fire was perhaps laid by the rescuer themselves to destroy what they found at the crash-site.
Since then things were never the same again in New Shoregate. Soon strangers came to the city and showed a peculiar interest into the HMS Arkham's mission and the events leading to her wreckage. There were rumors of unholy rituals near the crash site and at the local cemetery. Some kind of disease, so the locals said, started to spread, slowly corrupting everything getting contact with it. People started to suffer from mysterious symptoms and were haunted by unspeakable nightmares. Sometimes so horrifying that, upon waking up, they were so desperate that they committed suicide.
The following year became known as the 'Black Year' in the city's history. After the darkness of the winter-months, spring didn't bring light nor relief: The sun stayed a weak and pale under thick clouds, covering the city in a strange, alien twilight. Even the stars seemed to have come under some corrupting influence, as if they started shifting their positions, forming new unknown constellations
More and more people died from the disease. Soon the cemetery became too small for all the dead and the city council ordered that a mass grave should be dug instead. But the nearby swamp began to grow unnaturally fast, devouring the fair grounds and flooding the fresh burial site, bringing the dead back to the surface.
An exodus began: Many citizens left the city with the freight-ships which visited regularly and New Shoregate became more and more a ghost-town. The people who stayed barely dared to leave their houses anymore, because of the weird, unnatural noises from the swamp which could be heard all night long.
The city council sent out an expedition there to investigate the source of these noises, which returned with appalling stories of the things they have seen – or believed to have seen: corpses floating in the swamp, somehow still moving their decayed limbs and trying to free themselves from the mud. Some even said that the dead crouched towards them.
Last reports of survivors date from summer 1899. Since then, contact to New Shoregate has completely ceased. The Miskatonic University – while highly interested in the whereabouts of any survivors and of course the HMS Arkham and its cargo – strongly warns everyone visiting New Shoregate to expect the unexpected."
I think you should take this warning seriously - but visit the New Shoregate anyway!