This symbol of sovereignty was adopted on June 20, 1782 by the Second Continental Congress. Its imagery was finalized by Secretary of Congress Charles Thomson from design suggestions by Thomas Jefferson, John Adams, and Benjamin Franklin -- plus contributions from two other committees and from Thomson, who chose the American bald eagle as the centerpiece of the Great Seal.

Charles Thomson's remarks about the symbolism:

The Escutcheon [shield] is composed of the chief & pale, the two most honorable ordinaries. The Pieces, paly, represent the several states all joined in one solid compact entire, supporting a Chief, which unites the whole & represents Congress. The Motto alludes to this union.

The pales in the arms are kept closely united by the chief and the Chief depends upon that union & the strength resulting from it for its support, to denote the Confederacy of the United States of America & the preservation of their union through Congress.

The colours of the pales are those used in the flag of the United States of America; White signifies purity and innocence, Red, hardiness & valor, and Blue, the colour of the Chief signifies vigilance, perseverance & justice. The Olive branh and arrows denote the power of peace & war which is exclusively vested in Congress.

The Constellation denotes a new State taking its place and rank among other sovereign powers.

The Escutcheon is born on the breast of an American Eagle without any other supporters to denote that the United States of America ought to rely on their own Virtue.

Glossary of Heraldic Terms used in the Blazon