The town itself may be a bit barren, but the books, notes, and other "evidence" compiled in the library have a few stories to share. 

The Goddess

According to a book of legends for children, a woman of ethereal beauty known as The Harvest Goddess - or just The Goddess came to Barrow's Point when it was a barren, empty land. Deciding this would not do, she began to weave - starting with the Celestial River, which stretched across the land and cut through the mountainside, opening it wide and releasing the soil onto the land. Upon the soil, she wove grasses and herbs, enough until she blanketed the whole of the canyon.

One day a man came across her, and was entranced by her beauty. "Why do you weave, for a land as hopeless as this?" He boasted. "There are people who would appreciate your talents much more in the village. I am its chieftain. Come back with me and be my wife."

"I will not," she answered. "For I do not want appreciation for what I do. It is enough to know I am needed here." 

"But Goddess," he persisted, "Who is here to need you? The moon? The fish in the sea? It is the people that need you. Come back with me and be my wife."

"I will not," she answered once more, "For the people are clever and crafty. They draw soil from the riverbeds and wheat from the earth. They unite them when I cannot. They do not need me."

"But Goddess," he pleaded, "I need you. Come back with me and be my wife."

"I will not," she answered. "For I have told you three times no, and you continue to ask. It is your ego that needs me. Not your heart."

"Then I will destroy all that you have."

"You may try."

And so the man left, and returned the next day to razed the fields the goddess had woven. But not a season later, the plant life had grown back, healthier and more robust than before.

He had the people dam the river, by by the mountain passage, so that it would run dry. But within another season, the lake had filled and the dam had burst, and the river surged through once more.

At last, he came for the Goddess. But in the time it had taken for his people to harm her other creations, she had plucked the stars themselves from the sky and woven them into a grand staircase. She ascended the stairs to the skies beyond, and when he tried to follow, they shattered underfoot. As the shards of the star-steps filled the ocean shore, glowing in reflection for their siblings above them, the man asked one last time - "Why do you leave, Goddess? I have tried to ruin your fields and dam your river, and yet they have come back. Why would you leave a place so rife with potential?"

To which she turned her head and said, "Because I am no longer needed here." 

And across the stars, the Goddess departed, never to be seen again. But if you were to offer Her flowers to Her river, so that they may intermingle and weave their way into the great sea, she may smile upon you for uniting her creation. 

"K"

Considering the odd nature of the observatory and... well, just about everything strange that happens around Barlow's Point... the sender of the original message has been proposed to have either been a wizard capable of communing with the dead, or...  perhaps just a really strange old astronomer with a thing for idolatry. 

Whatever the case might have been, there's some fairly substantial evidence in the town's records that a man by the name of Kincade had lived alone in his observatory by the sea... for several years predating the town... and certainly well beyond when you logically should have received that postcard. Something fishy is definitely going on there.

What happened to the townsfolk?

Hard to say, unfortunately. A number of their personal books and diaries have found their way up into the library without any clear reason, but nothing is mentioned in any of them that offers any clue as to why that many people should have left (or disappeared) on the scale that they did.