Vessel documentation is a national form of registration with the United States Coast Guard.
It is one of the oldest functions of Government, dating back to the 11th Act of the First Congress. Documentation provides conclusive evidence of nationality for international purposes, provides for unhindered commerce between the states, and admits vessels to certain restricted trades, such as coastwise trade and the fisheries. Preferred Mortgages on documented vessels have been available since 1920 for vessel financing. A vessel must measure at least five net tons and must be wholly owned by a citizen of the United States. There are certain exceptions that apply.