Gadsden left no record of why he chose the rattlesnake, although it was already established in his home city of Charleston as a symbol of defense and vigilance. One patriot there called it a “noble and useful” animal, and it was drawn there and elsewhere on militia flags and drums.
Benjamin Franklin made the snake an icon of America in his 1754 cartoon “Join, or Die,” depicting the colonies as severed segments of a serpent. This illustration was much reproduced in the years since and is elaborated upon by Franklin in the Pennsylvania Journal on Dec. 27, 1775:
”She has no eye-lids. She may therefore be esteemed an emblem of vigilance. She never begins an attack, nor, when once engaged, ever surrenders…The Rattle-Snake is solitary, and associates with her kind only when it is necessary for their preservation.
“Tis curious and amazing to observe how distinct and independent of each other the rattles of this animal are, and yet how firmly they are united together, so as never to be separated but by breaking them to pieces.
“The power of fascination attributed to her, by a generous construction, may be understood to mean, that those who consider the liberty and blessings which America affords, and once come over to her, never afterwards leave her, but spend their lives with her.”