In 1849, the discovery of gold in California created a demand for speed that resulted in the creation of the clipper ship, a fast sailing ship with multiple masts and a square rig. The most important vessel built at the Mystic River Shipyard was the clipper ship "Andrew Jackson". In 1859, it sailed from New York City to San Francisco in a record time of 89 days and 4 hours. Both clippers and sailing packets were built in the shipyards of the Mystic River at that time. The Mystic shipyards started building ships with a greater cargo capacity after the Civil War.