Earle grew up on a Montgomery County estate as the son of George Howard Earle, Jr. and Catharine H. French, a wealthy family that traced its lineage in America to the arrival of the "Mayflower". His grandmother Mrs. Frances ("Fanny") Van Leer was a member of one of the first Pennsylvania families, the Van Leer family and his great-grandfather Samuel Van Leer played an important role in the American Revolutionary War. He received a degree from Harvard University and subsequently worked abroad in a family-owned sugar business. He enlisted in the military in 1916 and was assigned to the Mexican border during the Pancho Villa Expedition. After the United States entered World War I, Earle commanded , a submarine chaser which was also his private yacht. He earned the Navy Cross in 1918 after averting a fatal explosion. After the war, Earle returned to private business, particularly in the sugar industry. Though raised as a Republican, Earle joined the Democratic Party over disillusionment with the Republican Party's handling of the Great Depression. After campaigning for Franklin Roosevelt in the 1932 election, Earle served as Ambassador to Austria from 1933 to 1934. Earle looked warily upon the Nazi Party, and warned the FDR Administration of the potential danger of Nazi Germany.