"Cyrus was the fourth child of William and Sarah Ada Adair Mangum. He was born in Itawamba County, Mississippi on September 29, 1840. In 1845, Cyrus' parents joined the Church of Jesus Christ of Latter Day Saints. They moved to Nauvoo, Illinois on March 20, 1846. This was a traumatic time for the "Saints" as well as for the Mangum family. They found the city in a state of confusion. In early February of 1846, the first of the Saints began leaving Nauvoo for the Rocky Mountains. This put the Mangum family in the middle of this exodus. Cyrus was nearly five years old. One week later they crossed the Mississippi River. They traveled west to Mt. Pisgah, Iowa, where they lived for several years. In 1850 his family moved to Council Bluffs, Iowa. In 1852, the family began their trek to the west. In June of 1852, his baby sister died of cholera and was buried at the Bongo River. The migration continued despite their heartache. Fifteen days after his baby sister's death, his mother Sarah was found with the dreaded disease. Her death came quickly. She was buried along the banks of the Platte River near Loop Fork. They prepared a coffin for her by stripping bark from a large tree. They placed her body between two large strips of bark and tied the ends together. After her burial, his father's family moved on with the Saints with the hope there would be a brighter day.
The Mangum family arrived with a group of Saints in the valley of the Great Salt Lake on September 23, 1852. Within a few days they went on to Brigham City where they settled in the spring of 1853. On March 3, 1857, his father William, was called to help settle Utah's Dixie.
It was in the St. George area that Cyrus met Sarah Allen, a convert to the church from Australia. They were married November 8, 1861. His father William preformed the ceremony with her father acting as witness. Sarah's parents were Richard George Allen and Ester Elizabeth Hayes. The young couple went to San Bernardino to live for a short time. Here their first child was born. They later moved to Nephi, Utah where they made their home. Cyrus discovered a salt spring coming out of Mt. Nebo. In addition to farming, he mined salt from the spring to make their living. He and Sarah were active in church and civic affairs, and had many friends. They both had lovely singing voices and dramatic ability. Their remaining children were born there. Cyrus married a plural wife, Mary Tranter, the daughter of Thomas Tranter and Sarah Collins. Cyrus and Mary had at least eight children.