William Jack was born in Greensburg, Pennsylvania. He studied law, was admitted to the bar and practiced.
Early career
He moved to Brookville, Pennsylvania, in 1831 and engaged in mercantile pursuits. He was the division inspector of militia for Westmoreland and Fayette Counties from 1830 to 1835. He served as sheriff of Brookville in 1833, and was a contractor and builder in Mississippi and assisted in the construction of a canal there. He returned to Pennsylvania and served as a county judge of Jefferson County, Pennsylvania, about 1840.
Congress
Jack was elected as a Democrat to the Twenty-seventh Congress.
Later life
After his time in Congress, he was engaged in agricultural pursuits.
Death and burial
He returned to Greensburg in 1846 and died there in 1852. Interment in the Old Cemetery of the St. Clair Cemetery Association.
