Born on April 12, 1757, near Charlestown, Cecil County, Province of Maryland, British America,[1] Key pursued an academic course.

[3] After the war, Key went to England and graduated from the Middle Temple in London in 1784 and read law in 1785.

[1] Following his departure from the federal bench, Key resumed private practice in Montgomery County, Maryland from 1802 to 1807,[1] also engaging in agricultural pursuits.

[2] He served as counsel for Associate Justice of the Supreme Court of the United States Samuel Chase during his Senate impeachment trial in 1805.

[2] Following his departure from Congress, Key resumed private practice in Georgetown, D.C. (then a separate municipality in the District of Columbia, now a neighborhood in Washington, D.C.) from 1813 to 1815.