Margaret Thatcher, leader of the Conservative Party, becomes Britain’s first female prime minister on May 4, 1979. The Oxford-educated chemist and lawyer took office the day after the Conservatives won a 44-seat majority in general parliamentary elections.

Margaret Hilda Roberts was born in Grantham, England, in 1925. She was the first woman president of the Oxford University Conservative Association and in 1950 ran for Parliament in Dartford. She was defeated but garnered an impressive number of votes in the generally liberal district. In 1959, after marrying businessman Denis Thatcher and later giving birth to twins, she was elected to Parliament as a Conservative for Finchley, a north London district. During the 1960s, she rose rapidly in the ranks of the Conservative Party and in 1967 joined the shadow cabinet sitting in opposition to Harold Wilson’s ruling Labour cabinet. With the victory of the Conservative Party under Edward Heath in 1970, Thatcher became secretary of state for education and science.

In 1974, the Labour Party returned to power, and Thatcher served as joint shadow chancellor before replacing Edward Heath as the leader of the Conservative Party in February 1975. She was the first woman to head the Conservatives. Under her leadership, the Conservative Party shifted further right in its politics, calling for privatization of national industries and utilities and promising a resolute defense of Britain’s interests abroad. She also sharply criticized Prime Minister James Callaghan’s ineffectual handling of the chaotic labor strikes of 1978 and 1979.

In March 1979, Callaghan was defeated by a vote of no confidence, and on May 3 a general election gave Thatcher’s Conservatives a majority in Parliament. The next day, Prime Minister Thatcher immediately set about dismantling socialism in Britain. She privatized numerous industries, cut back government expenditures, and gradually reduced the rights of trade unions. In 1983, despite the worst unemployment figures for half a decade, Thatcher was reelected to a second term, thanks largely to the decisive British victory in the 1982 Falklands War with Argentina.

In other foreign affairs, the “Iron Lady” presided over the orderly establishment of an independent Zimbabwe (formerly Rhodesia) in 1980 and took a hard stance against Irish separatists in Northern Ireland. In October 1984, an Irish Republican Army (IRA) bomb exploded at the Conservative Party conference in Brighton. The prime minister narrowly escaped harm.

In 1987, an upswing in the economy led to her election to a third term, but Thatcher soon alienated some members of her own party because of her poll-tax policies and opposition to further British integration into the European Community. In November 1990, she failed to received a majority in the Conservative Party’s annual vote for selection of a leader. She withdrew her nomination, and John Major, the chancellor of the Exchequer since 1989, was chosen as Conservative leader. On November 28, Thatcher resigned as prime minister and was succeeded by Major. Thatcher’s three consecutive terms in office marked the longest continuous tenure of a British prime minister since 1827. In 1992, she was made a baroness and took a seat in the House of Lords.

In later years, Thatcher worked as a consultant, served as the chancellor of the College of William and Mary and wrote her memoirs, as well as other books on politics. She continued to work with the Thatcher Foundation, which she created to foster the ideals of democracy, free trade and cooperation among nations. Though she stopped appearing in public after suffering a series of small strokes in the early 2000s, her influence remained strong. In 2011, the former prime minister was the subject of an award-winning (and controversial) biographical film, The Iron Lady, which depicted her political rise and fall. Margaret Thatcher died on April 8, 2013, at the age of 87.