"President Young had a vision of Joseph Smith, who showed him the mountain that we now call Ensign Peak, immediately north of Salt Lake City, and there was an ensign that fell upon that peak, and Joseph said, 'Build under that point where the colors fall and you will prosper and have peace."' (From an address given in the Tabernacle on June 20, 1869.)

President Joseph F. Smith provided a similar description 13 years later: "(Brigham Young) had before seen an ensign descend and light upon the mountain peak, which is now called from that circumstance — 'Ensign Peak' — which was an indication to him that this was the resting place God designed for his people." (From an address given in the Provo Tabernacle on Dec. 3, 1882.)

The Mormon pioneers arrived in Utah on Saturday, July 24, 1847. They spent all of the next day, Sunday, resting and worshiping God. However, on July 26, one of the first tasks attempted was to climb what is now known as Ensign Peak to get a better look at the valley and probably also to see firsthand the mountain in President Young's vision.

Among those pioneers who made that first climb were Brigham Young, Heber C. Kimball, Willard Richards, Wilford Woodruff, George A. Smith, Ezra T. Benson, Albert Carrington and William Clayton. (The party used horses to make the first two-thirds of the climb, then dismounted and went on foot.)

Elder Woodruff was the first to reach the summit and President Young, still ill (and barely able to made it to the top with help), was likely the slowest climber. On top of the peak, President Young said, "Here is a proper place to raise an ensign to the nations." This is a reference to the scriptures where it mentions an "Ensign." (Isa. 5:26, D&C 105:39) These scriptural references are likely the inspiration for the peak's name.

The men then reportedly unfurled an ensign of liberty to the world. What an "ensign" means here is unclear. Perhaps the most common dictionary definition of an ensign is a flag or banner — specifically a national flag. But most historians are quick to point out that despite recurring myths, there's no evidence that a U.S. flag was raised on Ensign Peak at the climax of that first climb. Another definition of ensign is simply a badge or symbol, in accordance with a synonym of the word: insignia.

The pioneers did raise a U.S. flag in the valley below as early as October 1847, a significant act, since Utah was technically still Mexican soil. The U.S. flag was definitely flown on Ensign Peak, complete with a 21-gun salute, on July 24, 1897, from a special flagpole — about six months after Utah was admitted to the union — in commemoration of the 50th anniversary of the pioneers' arrival. A similar celebration was held on Ensign Peak, 50 years later in 1947.

Not long after the pioneers arrived in the Salt Lake Valley, Ensign Peak (probably the southern area below the peak, not the actual summit) was also used for a brief period as an outdoor temple until the Endowment House was constructed.