William B. Haskins was born around 1834 in Buffalo, New York, to Roswell and Emma Haskins. His father was a land agent. He grew up and attended school in Buffalo, and he moved to Groton, Massachusetts, in the 1850s. He worked as a bookkeeper, and by 1860, he owned $300 of personal property. He married Mary Ann Johnston on October 25, 1860, and they had at least two children: Charles, born around 1864; and Nellie, born around 1868.
He apparently chose not to enlist in the Union army, explaining that "we having wives, and especially, we who have had them for so short a time, can hardly make up our minds to leave them for the uncertainty of war." Nonetheless, he expressed devotion to the Union cause. In May 1861, he denounced a neighbor who was "too big a coward to fight for his countrys honor." He reassured a friend that "if you are called forth to fight, and it should be the fate of war, that you do fall, remember that it was in fighting for God and the right." He moved to Clark, Indiana, in the 1860s and then to Michigan City, Indiana, in the 1870s. By 1870, he owned $1,200 of real estate and $1,200 of personal property. He died in Manistee, Michigan, on November 18, 1897.