b. March 11, 1785, in Morris County, New Jersey; d. April 4, 1861, in Cincinnati, Ohio. McLean moved with his family to Virginia in 1789, to Kentucky in 1790, and to Ohio in 1796, where he worked on his family’s farm until the age of sixteen. In 1801, McLean moved to Cincinnati, Ohio, where he served as a clerk in the Hamilton County Court. With only two years of education, McLean studied law and gained admission to the bar in 1807. McLean moved his family to Lebanon, Ohio, where he published the Western Star in support of Thomas Jefferson and practiced law for four or five years. He was elected as a Democrat to Congress in 1812 and was reelected two years later. He resigned from his congressional seat in 1816, after the Ohio legislature elected him to the state supreme court. He remained on the bench until 1822, when President James Monroe appointed McLean as commissioner of the public land office, and in 1823, he appointed McLean postmaster general.

President Andrew Jackson nominated McLean as an associate justice of the United States Supreme Court, and the Senate confirmed his appointment on March 7, 1829. McLean presided over the Seventh Federal Circuit, which contained the states of Tennessee, Kentucky, and Ohio from 1830 to 1837. From 1837 to 1861, the Seventh Federal Circuit consisted of the states of Ohio, Indiana, Illinois, and Michigan. In the famous Dred Scott v. Sanford case, he dissented from the majority opinion of the Supreme Court. Although appointed by Jackson, Justice McLean favored the Whig Party and later identified with that portion of the Republican Party dominated by former Whigs. McLean maintained that a justice was under no obligation to refrain from political affairs, and he was frequently mentioned as a possible Republican presidential candidate, especially in the 1856 and 1860 campaigns. McLean maintained his seat on the Supreme Court bench until his death.