<P> In early March 1862, the blockade of the James River in Virginia was gravely threatened by the first ironclad, CSS Virginia in the dramatic Battle of Hampton Roads . Only the timely entry of the new Union ironclad Monitor forestalled the threat . Two months later, Virginia and other ships of the James River Squadron were scuttled in response to the Union Army and Navy advances . </P> <P> The port of Savannah, Georgia was effectively sealed by the reduction and surrender of Fort Pulaski on 11 April . </P> <P> The largest Confederate port, New Orleans, Louisiana, was ill - suited to blockade running since the channels could be sealed by the U.S. Navy . From 16--22 April, the major forts below the city, Forts Jackson and St. Philip were bombarded by David Dixon Porter's mortar schooners . On 22 April, Flag Officer David Farragut's fleet cleared a passage through the obstructions . The fleet successfully ran past the forts on the morning of 24 April . This forced the surrender of the forts and New Orleans . </P> <P> The Battle of Mobile Bay on 5 August 1864 closed the last major Confederate port in the Gulf of Mexico . </P>

How did the blockade affect the southern economy