'Old Ironsides' to fire guns on July 4

It's officially the USS Constitution, it's affectionately known as "Old Ironsides," and the Fourth of July is its day to shine.

The oldest commissioned warship in the world that's still afloat will sail from its berth at the Charlestown Navy Yard in Boston at 11 a.m. on Sunday. The crew will perform a 21-gun salute as it approaches Fort Independence on Castle Island, and later a 17-gun salute near the Coast Guard Station in Boston.

Launched in 1797, the Constitution won lasting fame with a series of victories over British warships in the War of 1812. It was retired from active service in 1855 and remains one of Boston's biggest tourist attractions, with more than a half million visitors each year.