In 1868, twenty years after the California Gold Rush, a small island off the coast of Northern California was purchased by a medical doctor named William Ambrose who wanted to establish a leper colony there. The island was known as Isla de la Roca at that time and was completely unpopulated, a perfect place for such a project. William had lost his daughter to the ravaging disease of leprocy only two years before, and the way she was treated during life convinced him that he had to create a place where those afflicted with the disease could find refuge. He renamed the island, using his own name and classifying the island as private property to deterr boaters from venturing ashore and disturbing the colony.

Soon there was an established leper colony on the island and William found joy in helping other victims where he couldn't help his daughter. However, the colony was not to last forever as in the winter of 1876 the worst storm in the island's history hit hard and fast. After the terrible storm passed no survivor was found on the island, and the land in turn passed to William's son Edward, who resided on the mainland. It was not in Edward to re-establish the colony there, so the colony was reclaimed by nature and the island remained uninhabited.

In 1898, thirty years since its initial founding and twenty-two years after the population was wiped out, Edward decided there was no use holding on to the island and decided to put it up for auction. As private islands in that area of the world weren't always easy to come by in that time, the land was purchased quickly. Its buyers were the wealthy Archibald and Helena Morrison, who knew nothing of the island's history other than that it was originally owned by William Ambrose. Edward had wisely left the leper colony out of his description of the island for fear that superstition might bring down the price.

The Morrisons kept the name Ambrose Island and built a large estate on the island. They had never intended to live as recluses, as they had several small children, so they began using their money to develop the land. In turn, they ended up making a profit when they sold it as both residential and commercial real estate, and slowly the private island became a community. Eventually, the Morrisons let go of their ownership of the island and it became part of the state of California, fulfilling the growing town's need for educational and emergency services that only the state could provide.

Now, in the early part of the twenty-first century, Ambrose Island boasts a population of just over 5000 residents, with that number reaching up to 10,000 at mid-summer, when tourists flood the little island for a taste of a slower, more quaint way of life than the one they're used to.