Philip A. Simpson was born around 1844 in Illinois to James and Lucretia Simpson. His father was a farmer who owned $12,500 of real estate and $500 of personal property. Simpson grew up in Menard County, Illinois, and by 1860, he was working as a farm laborer. He enlisted in the Union army on February 24, 1862, and mustered in as a private in Company K of the 28th Illinois Infantry. He died in Natchez, Mississippi, on September 29, 1863.