William Henry Greenleaf was born in Allegheny, New York, on December 7, 1834, and he was the son of William and Elmira (Sanford) Greenleaf. When he was eight years old, in 1843, he moved with his parents to Jefferson County, Wisconsin, and they settled on a farm. When William had grown to seventeen, he attended school at the Fort Atkinson Academy studying civil engineering. In 1856, during the troubles in Kansas, he made a trip to that territory with a group of men raised by a Professor Daniels, for the assistance of the Free Soilers. Greenleaf returned to Wisconsin, where, in 1857, he was employed as a surveyor on the Wisconsin Central railroad.