Year adopted: 1905, admitted to the Union 1889, as the 41st state. The area of Montana was annexed to the United States with the Louisiana Purchase of 1803.  Portions of the area were organized under both the Nebraska and Dakota Territories. The Montana Territory was then incorporated in 1864 and existed until Statehood in 1889.

The official flag of the State of Montana contains a reproduction of the Great Seal of the State in color on a field of deep blue, with gold fringe along the upper and lower borders. Although the flag was carried in the Philippines by the Montana Volunteers in the Spanish-American War in 1898 and was for many years considered the state flag, official action did not come from Montana Legislators until the session of 1904. The original hand-made banner carried by the First Montana Volunteers in the Spanish-American War is preserved by the Historical Society of Montana. It is 60 X 44 inches overall; the dark blue silk of the field is tattered and somewhat faded. But the Great Seal, beautifully hand-embroidered into a heavy tapestry, is in perfect condition. The words "First Montana Infantry, U.S.V." are embroidered in white over the multi-colored Great Seal. A 3-inch gold fringe adorns the top and bottom of this historic banner.

When the Ninth Legislative Assembly gathered in Helena in 1905, Representative Jacob M. Kennedy of Silver Bow County introduced House bill 157 adopting the banner as the State's official flag, with the deletion of the Infantry designation. Kennedy's bill read: "The 'State Flag of Montana' shall be a flag having a blue field, with a representation of the Great Seal of the State in the center, and with golden fringe along the upper and lower borders of the flag; the same being the flag borne by the First Montana Infantry, U.S.V., in the Spanish-American War with the exception of the device, '1st Montana Infantry, U.S.V.'" the House of Representatives passed the bill without a dissenting vote on February 7, 1905, and the Senate concurred on February 19.

The flag proved to be difficult to manufacture since the Great Seal had to be reproduced in a perfect color register, and no specifications had been given as to the shade of blue in the field. The dark blue of the volunteer flag was copied as nearly as possible in reproductions. (sos.mt.gov, About the State Flag) The flag uses a representation of the inner portion of the Great Seal on a blue field with "MONTANA" in gold lettering above. The great seal of the state is as follows: a central group representing a plow and a miner's pick and shovel; upon the right, a representation of the Great Falls of the Missouri River; upon the left, mountain scenery; and underneath, the words "Oro y Plata". The seal is surrounded by these words, "The Great Seal of the State of Montana". (ref sos.mt.gov, About the State Seal)