Margaret Thatcher became the first female Prime Minister of the UK on May 4, 1979

Margaret Thatcher became the United Kingdom's first female prime minister on this day in history, May 4, 1979, at age 54 — and led the U.K. for nearly 12 years, earning the moniker "Iron Lady."

Margaret Thatcher was sworn in as the first female Prime Minister of Britain on May 4, 1979. Some worshipped her as a modernizer who transformed the country while others bitterly accused her of entrenching the divide between the rich and the poor. Take a look back at Thatcher's life and influential career.