William Erasmus Cooper was the second of ten children born of John Jordan Cooper and Louisa Say Cooper. William was born in Washington County, Florida, on December 21, 1855.
During the spring of 1856, when William was less than six months old, his parents, older brother, Henry Moses Cooper, and grandfather, Washington Arnold Cooper, moved from Washington County, Florida, to a basin off the Blackwater River in Santa Rosa County, Florida.
William Erasmus Cooper's siblings were Henry Moses Cooper born in 1852, John Robinson Cooper born in 1858, James Fountain Cooper born in 1861, Michael Raleigh Cooper born in 1864, Daniel Jordan Cooper born in 1867, Selimea Cooper born in 1869, Thomas W. S. Cooper born in 1872, Susannah Demmerrea Cooper born in 1875, and Joseph Franklin Cooper born in 1879.
William was a tall, big-boned man who worked his farm and also worked in the timber industry like his other brothers. At the age of sixteen, William was a member of the Mt. Olivet Branch of the Reformed Latter Day Saints Church in Santa Rosa County and was baptized on May 1, 1871, by T. W. Smith. He would later be ordained as a teacher at the age of twenty-three by his father, John Jordan Cooper, on October 5, 1878.
William traveled occasionally back to Washington County, Florida, to visit his maternal grandmother, Selimea Slay, and other relatives. On occasion he would visit his Uncle James Jordan who was married to one of his mother's younger sisters. In one of the letters that his Uncle James Jordan wrote to him in 1876, he answers William's inquiry about the young women in the area. His Uncle James told William that there were plenty of pretty women in Washington County who were looking for sweethearts and would be interested in him; William and his younger brother James Fountain Cooper were urged to come for a visit.
On December 31, 1877, William married his sweetheart Winnie Bloodworth from Dale County, Alabama. William was twenty-two and Winnie was twenty-seven. Less than a year later, William's younger brother John Robinson Cooper married one of Winnie's younger sisters, Martha Dorah Bloodworth. William and Winnie had four children during the fifteen years they were married. Their children's names were: Hettie Caroline Cooper born in 1878, Sarah Cooper born in 1879, John Williamson Cooper born in 1881, and Louisa Cooper born in 1889.
William died during the same great flu epidemic in 1892 that killed so many in the Cooper family in Santa Rosa County, Florida. William's final resting-place is in the old Cooper Cemetery east of Cooper Basin and near the eastern edge of the old Cooper Homestead. Other members of William's family who died during the flu epidemic were his father, John Jordan Cooper, and his oldest brother Henry Moses' wife and oldest child, Elizabeth Reed Cooper and Henry Cooper. One of William's younger brothers, John Robinson Cooper, also lost his wife, Martha Dorah Bloodworth Cooper, and one of their sons, Johny Cooper. William's maternal grandmother Selimea Thompson Slay also died during the flu epidemic.
Winnie lived another forty-seven years after William's death and never remarried. She died on September 8, 1939, and her final resting-place is next to her youngest daughter, Louisa, in the Bagdad Cemetery in Bagdad, Florida.