John Nelson served as U.S attorney general from 1843 to 1845 under President John Tyler. In a long life of public service, Nelson served as a congressman and a diplomat, as well as an interim secretary of state. Nelson was born on June 1, 1791 in Frederick, Maryland. He graduated from the College of William and Mary in 1811 and then studied law under the guidance of lawyers in Virginia and Maryland. This type of legal apprenticeship was common at the time and led to Nelson's admission to the Maryland bar in 1813. Upon admission, Nelson established a private law practice in Frederick.

Nelson soon became active in Democratic Party politics and was elected in 1820 to the U.S. House of Representatives. He did not run for reelection in 1822 but in 1828 supported the presidential candidacy of Andrew Jackson. Jackson rewarded Nelson in 1831 by appointing him to a diplomatic post in Naples. Until 1832 he...