James Shields, born on May 12, 1806, emigrated from Ireland as a young man. Before settling in America he had numerous adventures as a sailor; he decided to settle in the United States after his legs were broken in a rigging accident in New York City. The enterprising youth eventually settled in Kaskaskia, the capital of the Illinois Territory. He taught school, studied law, and was admitted to practice.

He served in the Illinois House of Representatives in 1836, became the state auditor in 1839, and was a member of the Supreme Court of Illinois from 1843 to 1845. While serving in the Illinois House, Shields met Abraham Lincoln and Stephen A. Douglas. Lincoln was a Whig and Shields was a Democrat; the two clashed rhetorically and once even scheduled a duel. Shields served in the Mexican War and was injured in the Battle of Cheruhisco. He served briefly as governor of the Oregon Territory before being elected to the U.S. Senate, where he represented Illinois for one term. Defeated for re-election, he then moved to Minnesota, where he served from 1858 to 1859 as one of the first senators from that state. During the Civil War Shields served as a brigadier general with the Union Army.

After the war he continued his active political life. He was a member of the Missouri legislature and served as senator from Missouri in 1879, thus becoming the only senator to have represented three states. He died in office on June 1, 1879.