The circular Seal of the State of Colorado is an adaptation of the Territorial Seal, which was adopted by the First Territorial Assembly on November 6, 1861. The only changes made in the Territorial Seal design were the substitution of the words, "State of Colorado" and the figures "1876" for the corresponding inscriptions on the Territorial Seal. The first General Assembly of the state of Colorado approved the adoption of the state seal on March 15, 1877. The Colorado Secretary of State alone is authorized to affix the Seal of Colorado to any document.
By statute, the seal is two and one-half inches in diameter with the following devices inscribed: At the top is the eye of God within a triangle, from which golden rays radiate on two sides. Below the eye is a scroll, the Roman fasces, a bundle of birch or elm rods with a battle axe bound together by red thongs and bearing on a band of red, white and blue, the words, "Union and Constitution." The Roman fasces is the insignia of a republican form of government; the bundle of rods bound together symbolizes strength which is lacking in the single rod. The axe symbolizes authority and leadership. Below the scroll is the heraldic shield bearing across the top three snow-capped mountains on a red background with clouds above them. The lower half of the shield has two miner's tools, the pick and sledge hammer, crossed on a golden ground. Below the shield in a semicircle is the motto, "Nil Sine Numine,” Latin for "nothing without the Deity.” The year Colorado became a state, 1876, is printed at the bottom of the seal.
The design for the Territorial Seal which served as a model for the State Seal or Great Seal of Colorado has been variously credited, but the individual primarily responsible was Lewis Ledyard Weld, the Territorial Secretary, appointed by President Lincoln in July of 1861. There is also evidence that Territorial Governor William Gilpin also was at least partially responsible for the design. Both Weld and Gilpin were knowledgeable in the art and symbolism of heraldry. Elements of design from both the Weld and Gilpin family coat-of-arms are incorporated in the Territorial Seal.