In the fall 1775 the Continental Navy was established by George Washington and he named Esek Hopkins as Commodore of the Navy.
Before the departure of that first mission in December 1775, Hopkins received the flag from Gadsden & the iconic flag was born.
In 1751 Ben Franklin made the 1st reference to the rattlesnake in the Pennsylvania Gazette. Interestingly enough, immigration (of a sort) was at issue.
It's the first recorded mention of the future Gadsten flag symbolism.