In the United States, longshoremen generally find work through their local dockworker union. Two of the largest unions serving longshoremen include the International Longshoreman's Association and the International Longshore and Warehouse Union.
New longshoreman generally begin work as "unidentified casual" employees which means they are the last to be chosen for a job on a given day. After logging enough shifts at this stage, workers are invited to advance to the next stage of employment. Individuals who work in an area where there is a lot of shipping are much more likely to find work when they are at the unidentified casual stage.