A June 23 letter, "Respect 'rockets' red glare,'" from William T. Stokes, explained/justified the use of fireworks with an implication that "the rockets' red glare" and "bombs bursting in air" had something to do with Independence Day.
In a June 28 letter, "America's history revisited," Barbara Chester wrote that her grammar school teachers taught her independence with stories "about Francis Scott Key, the bombing of Fort Sumter and the beginning of the Civil War."
Fireworks for celebrations have a history far older than 1776. They were used on the first anniversary of the Declaration, in 1777, and have been a cause of contention ever since.
Key's poem, which became the national anthem in 1931, was written about the British siege of Fort McHenry, in Baltimore, in 1814 during the War of 1812. The tattered star-spangled banner Key wrote about is in the Smithsonian.