He was born February 28, 1853 in Prussia. His father Friedrich Wilhelm Lehmann emigrated to Cincinnati, Ohio, when Frederick was two, where he ruled the family with an iron hand. His mother Sophia died young.
At age 10, Frederick ran away from home forever. As a vagabond, selling newspapers, working on farms, and herding sheep, he wandered across the Midwest, rarely going to school. In his teens, at the urging of his fellow sheep men, he took the stump for presidential candidate Horace Greeley and gave his first political speech.
A noted orator, he was active in Iowa politics, including the election of Governor Horace Boies. In 1890 he moved with his family to St. Louis, Missouri and continued to represent the Wabash while building a general law practice. In 1908 he was elected president of the American Bar Association and served twice.
Representing the U. S. government in the Supreme Court, he would "confess judgment", a practice in which the Solicitor General admits that the government has been wrong all along and just drops the case even when supported by a lower court's prior decision. Inscribed in the office rotunda of the Attorney General is Lehmann's famous saying: "The United States wins its point whenever justice is done its citizens in the courts."
Frederick Lehmann always refused to run for public office, especially at a party convention of the breakaway Gold Democrats (opposed to the Free Silver candidate William Jennings Bryan) in St. Louis which he chaired (being foreign-born, he could not run for President anyway), and he declined judgeships. In politics he was generally a Democrat, if sometimes a Gold Democrat. In 1909 he drafted the charter by which the City of St. Louis is still run today.
In old age he auctioned off his rare book collections. He died September 12, 1931, aged 78, survived by his wife and three sons, lawyers Sears Lehmann, Frederick W. Lehmann, Jr., and John Stark Lehmann.
Three special collections at Olin Library, Washington University in St. Louis, include a selection of Lehmann's legal papers (including his time as Solicitor General), a collection of historic manuscript letters of notable people, and rare editions of works of Robert Burns and others. There is also a Frederick Lehmann Autograph Collection at the Missouri Historical Society, St. Louis.