Shanghaiing or crimping is the practice of kidnapping people to serve as sailors by coercive techniques such as trickery, intimidation, or violence. Those engaged in this form of kidnapping were known as crimps. The related term press gang refers specifically to impressment practices in Great Britain's Royal Navy.
Crimps flourished in port cities like London, Bristol and Hull in England and in San Francisco in California, Portland and Astoria in Oregon, and Seattle and Port Townsend in Washington. On the West Coast, Portland eventually surpassed San Francisco for shanghaiing. On the East Coast, New York easily led the way, followed by Boston, Philadelphia, and Baltimore.
The role of crimps and the spread of the practice of shanghaiing resulted from a combination of laws, economic conditions, and the shortage of experienced sailors in England and on the American West Coast in the mid-19th century.
First, once a sailor signed on board a vessel for a voyage, it was illegal for him to leave the ship before the voyage's end. The penalty was imprisonment, the result of federal legislation enacted in 1790. This factor was weakened by the Maguire Act of 1895 and the White Act of 1898, before finally being eradicated by the Seamen's Act of 1915.
Second, the practice was driven by a shortage of labor, particularly of skilled labor on ships on the West Coast. With crews abandoning ships en masse because of the California Gold Rush, a healthy body on board the ship was a boon.