Klein, Jacob was born on September 1, 1845 in Hessen-Darmstadt, Germany. Son of John Martin and Caroline (Güth) Klein.
Educated St. Louis public schools and 2 years in high school. Bachelor of Laws, Harvard, 1871.
Admitted to bar at St. Louis, May 29, 1869. Judge of Circuit Court, City of St. Louis, 1889-1901. Member Klein & Hough.
Counsel of Mercantile Trust Company, August since 1901. President Lafayette Mutual Building Association President St. Louis Bar Association, 1901-1902, 1903-1904. Appointed by President, United States delegate Universal Congress of Lawyers and Jurists, 1904.