Francis P. Knowlton was born in 1840 in Crown Point, New York, to Thomas and Louisiana Knowlton. His father was a farmer who owned $2,500 of real estate and $200 of personal property by 1860. The family moved to Whitewater, Wisconsin, in the 1850s, and by 1860, Knowlton was working as a laborer.
He enlisted in the Union army on August 21, 1862, and he mustered in as a private in Company E of the 28th Wisconsin Infantry. The regiment took part in the Vicksburg campaign, and he was discharged for disability on August 9, 1863.
He returned to Whitewater after leaving the army, and he married Harriet Washburne on December 27, 1868. They had at least four children: Lucy, born around 1870; Minnie, born around 1873; Jesse, born around 1875; and Mary, born around 1877. He worked as a moulder, and by 1860, he owned $800 of real estate. They moved to Janesville, Wisconsin, in the 1870s, and then to Rockford, Illinois, around 1881.
He applied for a federal pension in May 1889 and eventually secured one. He suffered two strokes around 1890 and reportedly “never regained his health.” His condition deteriorated during the winter of 1909-1910, and he died on February 25, 1910.