William Pennell was a busy Knox County, Ohio, physician and writer of note. He was born in 1853 in Holmes County, Ohio, where he received his public school education. Pennell graduated from the College of Wooster in 1875, and that same year married Melvina M. Williams.
He received a degree in pediatric medicine from Western Reserve University in 1882. Dr. Pennell began his medical practice in Holmes County, coming to Knox County in about 1882. His wife, Melvina died in 1903, and in 1920 he married Anna Grace Ash. During his medical career, Pennell continued to pursue advanced medical training. He also was active in several medical associations, one of which was the American Medical Authors Association.