This is an 1861 Harper's Weekly engraving entitled "Preparing Merchant Vessels for the Blockade." When the Lincoln Administration declared the blockade, the U.S. Navy was desperate for anything that floated to make the blockade proclamation legally binding. In this particular engraving are ships purchased in New York City: the steamers Augusta, James Adger, Florida, Valley City, Hale, and Star and Stripes and the sail barks Arthur, Brazelero, and Gem of the Seas.
While not ideal warships, many of this ships already had proven sea keeping traits and did succeed in capturing a few blockade runners during the war. The Navy equipped most of the vessels with old 32-pounders
The Federal government ability to buy up so many ships demonstrated one of its "advantages" over its Southern opponent. With ready access to cash, the Federal government was able to buy whatever equipment it needed.