Smith was born into a Mormon family in Oswego, New York. At the age of 16, he joined a contingent of Latter-day Saints who fought for the United States in the Mexican War in California. He then moved to Utah, where he joined Brigham Young's Territorial Militia and saw action in several campaigns against Native Americans who were hostile to the Mormon settlers. Though Smith won praise as a loyal defender of the Mormon settlement in Utah, the precise nature of Brigham Young's theocratic community was unclear: Was Utah an independent nation or a territory of the United States?
During the 1850s, the ambiguous status of Utah led to an armed conflict between the United States Army and the Utah militia in which Smith played a central role. Determined to assert federal control over Utah, in 1857 President James Buchanan ordered U.S. soldiers to Utah to ensure Mormon loyalty and acquiescence to federal authority. That July, a force of soldiers that became known as the Utah Expedition left Fort Leavenworth, Kansas, and headed for Utah.
Young feared that the soldiers were not a legitimate federal army but rather an armed mob of anti-Mormon fanatics. He directed his Mormon militia to impede the progress of the U.S. Army. Fortunately, the Mormon militia found that the ill-prepared forces under the leadership of Colonel Albert Sidney Johnston were easily stymied without having to resort to actual combat. Now serving as a major in the Utah militia, Smith was able to capture and burn two of Sidney's provision trains of 52 freight wagons and drive off most of the oxen and beef. Brutal weather combined with the Mormon's effective destruction of his supply lines forced Johnston to retreat to Fort Bridger, Wyoming.
Smith's successful efforts, and those of other leaders of the Mormon militia, may have kept the conflict from turning into a full-scale war. By the following spring when Johnston's army again headed toward Salt Lake City, the passion for war on both sides had cooled. Brigham Young, who claimed he had always been loyal to the United States, accepted a new gentile governor for Utah Territory. If the Mormons had indeed once dreamed of creating an independent theocratic community in Utah, they now abandoned the idea and largely accepted federal authority.
For his part, Smith went on to play an important role in expanding Mormon settlement in the West, leading a successful effort to colonize northern Arizona. He became a forceful, and some said autocratic, leader of the Mormon settlement at Tuba City, where he established his Circle S Ranch and may have taken as many as eight wives.
In the 1890s, the Arizona Mormons came into increasing conflict with Navaho Indians who grazed their sheep on land that the Mormons claimed as their own. Smith apparently angered the Navaho by shooting several of their sheep he found grazing on land he claimed. On this day in 1892, a small band of Navaho retaliated by ambushing Smith and shooting him to death. He was 62 years old.