Dr. Anna Clark, professor of history at the University of Minnesota, discusses Margaret Thatcher's legacy to Great Britain. British Prime Minister Margaret Thatcher died yesterday at the age of 87. Born on October 13, 1925, in Grantham, England, Margaret Thatcher became Britain's Conservative Party leader and in 1979 was elected prime minister, the first woman to hold the position. During her three terms, she cut social welfare programs, reduced trade union power and privatized certain industries. Thatcher resigned in 1991 due to unpopular policy and power struggles in her party.