William Dwight Barrell was born around 1838 in Turner, Maine, to Jonathan Barrell and Abigail Carey. His father was a farmer who owned $1,075 of real estate and $668 of personal property in 1860. Barrell grew up and attended school in Turner. His mother died around 1858. By 1860, Barrell was working as a farmer, and he owned $1,000 of real estate and $50 of personal property.
He married Mary A. Parker in Turner on December 25, 1867, and they had at least three children; William, born around 1869; Frederick, born around 1877; and Mabel, born around 1880. They lived in Turner, and Barrell worked in a granite quarry. By 1870, he owned $1,300 of real estate and $700 of personal property. He became a local postmaster in 1889. He died in Turner on September 27, 1895.