Herta Ware Schwartz was born on June 9, 1917, in Wilmington, Delaware, to Helen Ware, a musician and violin teacher, and Laszlo Schwartz, an actor. Her father was a Hungarian Jewish immigrant from Budapest, and her mother was a many-generations American of colonial stock. Her maternal grandfather was a union activist who joined the Socialist Party in America during the early 1900s, her maternal grandmother was labor organizer and socialist Ella Reeve Bloor, and her uncle was activist Harold Ware.
As a child, Herta was a guitarist and folk singer in the Washington D.C. area, before moving to New York City and beginning her acting career in the early 1930s. She made her Broadway debut in the 1935 leftist play "Let Freedom Ring" co-starring future husband Will Geer, whom she married in 1938. The couple appeared together in other New York plays as well, including "Bury the Dead" (1936),"Prelude" (1936),"200 Were Chosen" (1936) and "Journeyman" (1938).
The couple relocated to Los Angeles in the early 1940s and settled in Santa Monica, where Geer pursued a movie career. They had three children, all future actors: Kate Geer, Ellen Geer, and Thad Geer. In 1951, the couple was blacklisted by Hollywood during the McCarthy era for taking the Fifth Amendment and refusing to testify before the House Un-American Activities Committee.