USS Anacostia was a steamer, constructed as a tugboat, that was first chartered by the United States Navy for service during the Paraguay crisis of the 1850s and then commissioned as a U.S. Navy ship. She later served prominently in the Union Navy during the American Civil War.

The Paraguay expedition (1858–1859) was an American diplomatic mission and nineteen-ship squadron ordered by President James Buchanan to South America to demand redress for certain wrongs alleged to have been done by Paraguay, and seize its capital Asunción if it was refused. The expedition was sent without an adequate investigation of the facts; most modern scholars have considered Buchanan's complaints were probably unjustified. The real cause of the misunderstandings was that neither country had employed a competent diplomatic service. Buchanan may have had an ulterior motive, such as to distract public opinion from the domestic concerns that afflicted his presidency, and yet more sinister explanations have been put forward; but possibly Buchanan may have meant to emulate the success of the earlier Perry Expedition, which had "opened up" isolated Japan.