Thatcher was the first woman to become U.K. prime minister and Britain's only prime minister of the 20th century to win three consecutive terms.
After leading the Conservatives to victory in the 1979 election, Thatcher shook Britain to its economic roots in a relentless battle to restructure the country.
Richard Longworth of the Chicago Tribune described Thatcher in 1989 as "perhaps the most admired, hated, fascinating, boring, radical and conservative leader in the Western world."
The next year she would be forced from office by her own party.
The mayor's daughter
Born Margaret Hilda Roberts in Grantham, England in 1925 she was the second daughter of Alfred and Beatrice Roberts. Her father eventually owned two grocery stores (the family lived above one of them) and would become mayor of Grantham.
He had a huge influence on Margaret, as she observed when she became prime minister.
- RELATED: Margaret Thatcher's death evokes polarized reaction
"Of course I just owe almost everything to my father. He brought me up to believe almost all the things I do believe."
She graduated from Oxford in 1947 after majoring in chemistry. She was barred from joining the all-male Oxford Union debating society, so she joined Oxford's conservative association and in 1946 became its first female president.
She ran for Parliament in 1950, the youngest person seeking a seat. She lost — and lost again the next year.
At the end of 1951 she married Denis Thatcher, a wealthy, divorced businessman she met in 1949.
Since graduating, Margaret had been working as a research chemist. She returned to university and earned a law degree in 1953. She gave birth that year to twins and continued to be politically active.
After being called to the bar she specialized in patent law and then tax law, until 1961.
Elected to Parliament on her third try
In 1959 she was elected as the MP from Finchley. Two years later then prime minister Harold Macmillan named her parliamentary secretary to the minister of pensions and insurance.
- RELATED: 7 memorable Margaret Thatcher quotes
From 1964 to 1970 the Labour Party governed and Thatcher held various portfolios in the opposition shadow cabinet.
When the Conservatives were back in power under Edward Heath, Thatcher was the secretary of state for education and science, the only woman in the cabinet. She got attention when she abolished a free milk program for school children, and was dubbed 'Thatcher the milk snatcher' by the Labour opposition.
Heath resigned as leader after losing the 1974 election and his successor was the first woman to lead the Conservatives, Margaret Thatcher.
"I am not a consensus politician. I am a conviction politician," Thatcher announced when she took over in 1975.
The Iron Lady
That kind of approach earned her the nickname the Iron Lady, which she wore proudly. That description originated in the Russian media after she harshly denounced Soviet expansionism and questioned the long-standing Western policy of detente with the Soviet Union in 1976.
Here's an example of how she turned the nickname to her advantage in the 1979 election campaign, at a rally in Birmingham: "We took that risk in 1976 when we warned the nation of the growing dangers of Soviet expansion. And what happened? The Russians said that I was an Iron Lady. They were right. Britain needs an Iron Lady."
Her campaign slogan was "Labour isn't working," a slogan that U.S. Republican presidential candidate Mitt Romney borrowed for his own campaign in 2012, "Obama isn't working."
Two years before she took the reins as Conservative Party leader, Thatcher said on the BBC: "I don't think there will be a woman prime minister in my lifetime."
But after winning the May 3, 1979 election, Margaret Thatcher became prime minister the next day.
Her victory followed six weeks of public sector strikes known as the winter of discontent, which caused deep difficulties for the Labour government and eventually led to its fall.
Once in office Thatcher slashed the tax rates for the wealthiest Britons, increased the value-added tax (VAT), reduced government subsidies and began to sell off state-owned enterprises and public housing.
The number of unemployed quickly doubled.
"We shall not be diverted from our course," she told the party conference in Brighton in 1980. She continued: "To those waiting with bated breath for that favourite media catchphrase the U-turn, I have only one thing to say: You turn if you want to. The lady's not for turning."
By March 1982, the Conservatives had fallen to third place in public opinion polls, with just a 22 per cent approval rating.
A bold decision to go to war
The next month, there was a huge opportunity to turn that plummeting support around: Argentina's military dictatorship seized the Falkland Islands, a British overseas territory in the South Atlantic Ocean, which Argentina also claimed.
If politics is the art of knowing what to do next, Thatcher showed she had the right stuff.
"I worried stiff. It was a decision which had to be taken, a very bold courageous decision," she recalled in a 1983 interview with the CBC's Barbara Frum.
- RELATED: Margaret Thatcher's death marked respectfully - and otherwise - on Twitter
A naval task force was quickly dispatched. After 10 weeks and the loss of 255 British lives, Argentina surrendered. "Great Britain is great again," Thatcher shouted to a jubilant crowd outside her residence.
Thatcher called an early election in 1983 and won a larger majority, although with a popular vote lower than in 1979.
Thatcher continued to forge ahead with her policies, known as Thatcherism. She succeeded in curbing union power, especially with the defeat of the mineworkers in 1984-85.
She took on the Irish Republican Army, but had little success in solving the crisis in Northern Ireland. In 1984 the Provisional IRA tried to kill her by placing a bomb in her hotel in Brighton. Five people were killed, Thatcher's bathroom was destroyed, but she and her husband emerged unscathed.
In a 1986 profile of Thatcher in The New Yorker magazine, John Newhouse wrote: "Her policies are blamed for Britain's having become a net importer of manufactured goods — for the first time since the days of Henry VIII." Newhouse went on to note that, according to the IMF, the average Briton had become poorer than the average Italian.
Thatcher would stay the course. "This government has rolled back the frontiers of the state and will roll them back still further," she triumphantly declared at the party conference in October 1986. The unemployment rate was dropping at the time, although inflation was rising.
Close relations with Reagan, Gorbachev
Internationally, her close relationship with U.S. president Ronald Reagan continued. "We share so many of the same goals, and a determination to achieve them," she said at a joint appearance with Reagan in Washington in 1985.
She also formed a close relationship with Mikhail Gorbachev, who led the Soviet Union from 1985 to 1991. "I like Mr. Gorbachev, we can do business together," she famously told BBC interviewer John Cole in 1984.
Thatcher is also remembered for her refusal to join 48 other Commonwealth nations, including Canada, in implementing sanctions against the apartheid regime in South Africa.
In 1987, hoping to reap the benefits of her now considerable international standing, including a successful visit to Moscow, Thatcher again called an early election. She won a then-unprecedented third term, although the Conservative popular support dropped slightly to 42.2 per cent.
Her targets for rolling back the state now included health care, education and utilities. By 1988, while no longer operating with a deficit, her government cut tax rates, most dramatically for those in the top tier.
A cabinet coup d'etat
Her leadership style was stirring up dissent within her cabinet. One of the critical issues was the preparations for economic and monetary union in Europe, with Thatcher more or less opposed. Her chancellor of the exchequer, Nigel Lawson, would resign over the issue in October 1989.
The other issue was Thatcher's stubborn clinging to her plans for a community charge, damned as the poll tax. The tax outraged taxpayers, culminating in a riot in Trafalgar Square in March 1990. The Conservatives were trailing Labour by about 10 points in public opinion polls and unemployment was rapidly increasing again.
Geoffrey Howe, her deputy prime minister, resigned over both issues in November and followed that with a bitter speech critical of Thatcher's leadership.
The party was now in full crisis. In a challenge to her leadership later that month, Thatcher won on the first ballot but, with an insufficient level of support, she soon resigned as party leader and then, on Nov. 28, 1990, as prime minister.
Her voice breaking, she began her brief but final speech as prime minister: "We're leaving Downing Street for the last time after eleven-and-a-half wonderful years, and we're very happy that we leave the United Kingdom in a very, very much better state than when we came."
She continued to voice her opposition to greater European economic integration, causing problems for her successor, John Major.
In 1992, she was appointed a Life Peer as Baroness Thatcher of Kesteven, allowing her to sit in the House of Lords.
After a few years, and apart from promoting her books, she was not often in the public eye. One notable moment was in 1999 when she visited Augusto Pinochet in London. The former head of a brutal military dictatorship in Chile was being detained in London over war crimes charges.
In 2002, she announced she was retiring from public speaking, following a series of minor strokes. In 2003, her husband Denis died.
In 2008 her daughter Carol confirmed that Thatcher was suffering from dementia.
Loved or loathed, Thatcher's personal accomplishments will remain part of world history. In a 2007 radio address marking the end of the Falklands war, making use of an ancient Latin proverb, she told her listeners, "Fortune does, in the end, favour the brave."
Also on HuffPost