Montana is a state in the Mountain West division of the Western United States. It's the fourth-largest state by area, the eighth-least populous state, and the third-least densely populated state. Its state capital is Helena.

It became the 41st state of the U.S. on November 8, 1889. It has many state nicknames, but, the best known are "Treasure State" referring to the state’s natural resources, and "Big Sky Country" for Montana’s beautiful open country with far-reaching vistas.

The use of the name "Big Sky Country" as being directly associated with the state of Montana can be traced to an effective 1962 promotion by the Montana State Highway Department. One of the men who worked there had read the book "The Big Sky" wrote by American novelist, screenwriter, historian, and literary historian Alfred Bertram Guthrie Jr., which told the story of hunters working outdoors under the Big Sky.

The employee thought this would be a great phrase to use in the campaign to capture the state’s essence and appeal and received permission from Guthrie to use the name.

An ad from the campaign invited prospective tourists to “Travel Montana, the Big Sky Country, between Yellowstone and Glacier”. The phrase took hold because of the promotion, and Montana has been thought of as Big Sky country since that time.

The nickname "Big Sky Country" or shortened to "Big Sky" has also been featured in past years on the state’s official license plates, with an image of mountains and sky.

More Info: discoveringmontana.com