Fire destroyed much of the Library of Congress in 1851, highlighting the vulnerability of the rotunda’s wooden dome. The architect Thomas Walter designed a fireproof dome better suited to the growing building. On March 3, 1855, Congress authorized the cast-iron replacement. Workers removed the old dome and began installing the new one soon thereafter.
For years, the project’s supervising engineer purchased iron from various foundries—until the New York firm of Janes, Fowler, Kirtland & Company won the exclusive iron contract in 1860. When the Civil War broke out, the administration warned the company not to expect further payment. The firm proceeded nevertheless. This perseverance struck President Lincoln as a symbol that the Union, like the dome, would continue. Despite wartime conditions that drained manpower and materials, construction went ahead. Former slaves—including Philip Reid, who helped cast the Statue of Freedom that was placed atop the dome in December 1863—helped ease labor shortages.