When the war between the United States and Mexico ended in 1848, the American government subsidised private industry to build and operate two fleets of side-wheel steamers to connect the new territory of California with the rest of the country. One fleet would travel between New York and Panama, the other from Panama up to Oregon, with brief stops at outposts in San Diego, Monterey and San Francisco.
The original idea was for these steamers to travel every two weeks, carrying intelligence, mail, newspapers, express freight, and eventually passengers.
But when gold was discovered in the new state of California, these sea routes, and the ships that sailed them, took on a new importance.
Travelling east-west, the cargo was a human one, the hordes of people eager to make their fortunes in the gold fields, while returning west-east the ships were loaded down with the precious metal.
On Tuesday, September 8th, 1857, the SS Central America set sail from Havana harbour, having departed Panama four days earlier. Aboard were 500 passengers, plus a cargo of roughly 21 tons of gold.
For half a day the seas remained clear and calm, the breeze coming from the trade winds quarter and the surface smooth. Then the weather changed, thunder-heads gathered, and soon the crew was battling hurricane-force winds and 35-foot waves.
Water leaked into the hold, cooling the engines, the paddle-wheels ceased to turn and the ship began to flounder.
As the women and children huddled in the saloon, their men-folk bailed, but it was a losing battle and soon the Central America began to sink.
In the end some 428 people lost their lives, the gold going down with the ship and resting on the bottom of the ocean nearly 200 miles off the Carolina coast.
Author Gary Kinder gives an engrossing account of the time, the place and the event, but the actual sinking of the ship forms only the beginning of his story.
The main narrative is taken up with the efforts of one far-seeing man, Tommy Thompson, and the group of like-minded people he gathered around him, to delve down through the thousands of feet of water and salvage the gold and the artefacts that had lain on the floor of the ocean for over a hundred and twenty years.
But if his immediate goal was to find the fabled steamer and recover her treasure, his real purpose was to open the deep-ocean frontier to science, history, medicine, mining and archaeology.
For Thompson was a scientist who dreamed dreams, one who believed that limits were there to be pushed aside.
In the summer of 1988, he and his Columbus-America Discovery group went to sea to find the Central America with prototype sonar that enabled them to search 5,000 feet of ocean bottom in a single swath.
The following year he created a robot that could perform intricate, heavy and often delicate tasks in water over 8,000 feet deep. Eventually he was to fly his unmanned robot over the rusting remains of two huge paddle wheels; then he located the ship's 300 lb bell, steamer trunks, other artefacts, and finally the gold, carpeting the bottom of the ocean like a glittering garden.
The harvesting of the gold formed a saga of its own, with 39 insurance companies lining up to claim their share. After protracted court cases, Thompson's group was allotted 90 per cent of the treasure, but then descendants of the people who went down with the ship came out of the woodwork, and litigation is still pending.
Kinder's account of the adventure is compelling on many levels, not least for the fact that the scientists found in the deep ocean what they called "a bloom and pulse of life", a diversity of new life forms available for pharmaceutical testing, life forms that may well provide anti-cancer drugs called tumour inhibitors. And the work goes on.