His parents had immigrated to the United States from the German Confederation (now Germany) in 1855, and his father, Jacob Dietrich, became a farmer.

Jacob Dietrich died less than one year after the birth of his son Frank, whose name was chosen to honor American Civil War general Franz Sigel.

He taught Latin, history, and political science at Ottawa University in Kansas,[2] and read law to enter the bar in 1891, and was an attorney for the Union Pacific Railroad from 1899 to 1907.

[3] Dietrich was nominated by President Calvin Coolidge on December 22, 1926, to a seat on the United States Court of Appeals for the Ninth Circuit vacated by Judge Wallace McCamant.

[citation needed] The town of Dietrich in rural Lincoln County, Idaho was named after him shortly after he became a federal judge.