b. November 21, 1819, in Smyrna, Delaware. Prettyman came to Illinois at the age of twelve. From 1840 to 1844, he served as a deputy surveyor. He began the study of law under Judge Silas W. Robbins of Springfield, Illinois. Admitted to the bar in 1845, Prettyman moved to Pekin, Illinois, to practice law. He was associated with Lincoln in a number of Tazewell County court cases. Active in Democratic party politics, he served as chairman of the Tazewell County Democratic Committee for a number of years, and he was also a member of every Democratic National Convention from 1860 to 1892, except the convention of 1876. During the Civil War, he was elected mayor of Pekin, a position he held several times. Prettyman was also active as the director and vice-president of the Illinois River Railroad and as president of the Chicago, Pekin, and Southwestern Railroad.