William Penn Adair was born on April 15, 1830 in the old Cherokee Nation in New Echota, Georgia. His parents were George Washington Adair and Martha Adair. He attended Cherokee schools in Indian Territory, studying law. He was a Freemason, belonging to the Vinita Lodge No. 5, which was chartered in 1875. He was described as being "six foot and two inches in height, magnetic, logical and frankly agreeable, the ablest and most brilliant of all Cherokees.