He was Chief Judge of the New York Court of Appeals from 1883 until his death. William C. Ruger was educated at Bridgewater Academy, then studied law with his father, was admitted to the bar in 1845, and commenced practice in Bridgewater. In 1853, he removed to Syracuse, New York, formed a partnership with his father.
William C. Ruger was a delegate to the 1872 Democratic National Convention.
In November 1882, he was elected on the Democratic ticket Chief Judge of the Court of Appeals, and died in office in 1892. He was buried at Oakwood Cemetery (Syracuse, New York).