Fort Pulaski on Cockspur Island at the mouth of Georgia’s Savannah River was built from 1829 to 1847 as part of the United States’ post-War of 1812 coastal defense system and was long considered nearly impregnable. Named for Revolutionary War officer Casimir Pulaski, it became historically pivotal in the Civil War when Union rifled artillery breached its thick brick walls in 1862, proving masonry forts vulnerable to modern guns. Afterward, under Union control, it helped enforce the blockade of Savannah, became a refuge for people escaping slavery, later held Confederate prisoners, and eventually was preserved as a national monument.