John C. Dunwiddie was born around 1833 in Ohio to William and Margaret Dunwiddie. His father was a farmer who owned $1,200 of real estate by 1850. The family moved to Indiana around 1834, and he grew up and attended school in Coal Creek, Indiana. By 1860, he was working as a farmer in Oak Grove, Indiana, and he owned $680 of real estate and $300 of personal property.
He married Viletta Thomas on May 8, 1865, and their daughter Ora was born around 1871. They settled in Butler, Illinois, and by 1870, they owned $1,200 of real estate and $700 of personal property. They returned to Coal Creek in the early 1870s. His wife died in the early 1900s, and he died of pneumonia on March 17, 1918.