The son of a surgeon, James Clark McReynolds was born on February 3, 1862, in Elkton, Kentucky. He graduated from Vanderbilt University in 1882 and followed in the footsteps of the President he would serve, Woodrow Wilson, by studying law at the University of Virginia, earning his degree in 1884. McReynolds entered the political arena when he served briefly as private secretary to U.S. Senator Howell E. Jackson. He returned to his law practice in Nashville, Tennessee, before losing in a bid for Congress as a "gold" Democrat in 1896.

McReynolds taught law at Vanderbilt University from 1900 to 1903, at which time he was appointed assistant U.S. attorney general by President Theodore Roosevelt. As special counsel for the government from 1907 to 1912, McReynolds prosecuted violators of the Sherman Antitrust Act. President Woodrow Wilson named him attorney general on March 5, 1913.

When Associate Justice Horace Lurton resigned from the Supreme Court in August 1914, Wilson tapped McReynolds to take his place. McReynolds served on the high court for twenty-six years, until February 1, 1941, voting down most New Deal measures during the presidency of Franklin Roosevelt. He died on August 24, 1946, in Washington, D.C.