1941 - Japanese warplanes attack US fleet at Pearl Harbor in Hawaii; US declares war on Japan; Germany declares war on US, which thereafter intervenes on a massive scale in World War II, eventually helping to defeat Germany.
1945 - US drop two atomic bombs on Hiroshima and Nagasaki. Japan surrenders.
1947 - US enunciate policy of aid for nations it deems threatened by communism in what became known as the Truman Doctrine. Cold War with Soviet Union begins.
1948 - America's program to revive ailing post-war European economies - the Marshall Plan - comes into force. Some $13bn is disbursed over four years and the plan is regarded as a success.
1950-54 - Senator Joseph McCarthy carries out a crusade against alleged communists in government and public life; the campaign and its methods become known as McCarthyism. In 1954 McCarthy is formally censured by the Senate.
1950-53 - US forces play leading role against North Korean and Chinese troops in Korean War.
Desegregation and the Vietnam War
1954 - Racial segregation in schools becomes unconstitutional; start of campaign of civil disobedience to secure civil rights for Americans of African descent.
1960 - Democratic Party candidate John F Kennedy elected president, narrowly defeating his rival Richard Nixon.
1961 - Bay of Pigs invasion: an unsuccessful attempt to invade Cuba by Cuban exiles organized and financed by Washington.
1962 - US compel Soviet Union to withdraw nuclear weapons from Cuba in what has become known as the Cuban missile crisis.
1963 - President John F Kennedy assassinated; Lyndon Johnson becomes president.
1964 - US steps up its military intervention in Vietnam. Civil Rights Act signed into law; it aims to halt discrimination on grounds of race, color, religion, nationality.
1968 - Black civil rights leader Martin Luther King assassinated.
1969 - Republican Party candidate Richard Nixon elected president amid growing public opposition to Vietnam war. US military presence in Vietnam exceeds 500,000 personnel.
US astronaut Neil Armstrong becomes the first person to walk on the Moon.
1972 - Nixon re-elected and makes historic visit to China.
1973 - Vietnam ceasefire agreement signed. The campaign had claimed some 58,000 American lives.
1974 - In a TV address, Nixon announces his resignation in the wake of the Watergate scandal, over a 1972 break-in at the Democratic Party headquarters. Gerald Ford is sworn-in as his successor.
1976 - Democratic Party candidate Jimmy Carter elected president.
1979 - US embassy in Tehran, Iran, seized by radical students. The 444-day hostage crisis - including a failed rescue attempt in 1980 - impacts on Carter's popularity and dominates the 1980 presidential election campaign.
1980 November - Republican Party's Ronald Reagan elected president. Reagan goes on to adopt a tough anti-communist foreign policy and tax-cutting policies which lead to a large federal budget deficit.
1981 January - Iran frees the 52 US embassy hostages, on the same day as President Reagan's inauguration.
1983 - US invades Caribbean nation of Grenada, partly prompted by its concerns over the island's ties with Cuba.
1984 - Ronald Reagan re-elected president, beating Democratic Party candidate Walter Mondale.
1986 January - Space shuttle Challenger explodes shortly after take off from Cape Canaveral. All seven crew members are killed. Manned space flights are suspended until September 1988.
1986 - US warplanes bomb Libyan cities. "Iran gate" scandal uncovered, revealing that proceeds from secret US arms sales to Iran were used illegally to fund Contra rebels in Nicaragua.
1994 - Congress defeats Clinton's flagship legislation intended to reform health care system.
1994 - Investigations into Whitewater scandal, over the Clintons' financial dealings in Arkansas, where he had been governor before becoming president. Sexual harassment charges are filed against Clinton by a former Arkansas employee. Mid-term elections result in Republican majorities in both houses of Congress.
1995 - Oklahoma bomb kills more than 160 people in worst ever incident of its kind in US.
1996 - Clinton re-elected, beating Republican rival Bob Dole.
1998 - Scandal over Clinton's purported sexual impropriety with White House worker Monica Lewinsky dominates domestic political agenda and leads to impeachment proceedings in Congress.
1999 February - Clinton acquitted in Senate impeachment trial.
1999 March-June - US plays leading role in NATO bombardment of Yugoslavia in response to Serb violence against ethnic Albanians in the province of Kosovo.
2000 November - Vice-president and Democrat candidate Al Gore and the Republican Party's George W Bush contest one of the closest presidential election races ever. Bush is initially declared the winner in the crucial state of Florida, but the margin is so small that there is an automatic recount. The Democrats mount a series of legal challenges which eventually involve the Supreme Court. Bush is finally declared the winner in Florida, which enables him to take the presidency, albeit with a smaller share of the national vote than Gore.
2001 January - George W Bush sworn in as 43rd president of the US.
2001 April - US reconnaissance plane forced to land in China after mid-air collision with Chinese fighter jet; crew held by Chinese authorities for 11 days. Angry diplomatic exchanges take place between Washington and Beijing.
2001 July - US tests its controversial missile defense shield, or "Son of Star Wars".
11 September attacks
2001 11 September - Four passenger aircraft are hijacked and crashed into the World Trade Center in New York, the US Defense Department - the Pentagon - in Washington DC and into a field in Pennsylvania; 3,025 people are killed in the attacks.
2001 8 October - US leads massive campaign of air strikes against Afghanistan and later sends in special forces to help opposition forces defeat the Taliban regime and find Saudi-born dissident Osama Bin Laden, who is suspected of masterminding the 11 September attacks.
2001 October - USA Patriot Act approved by the Senate, giving the government greater powers to detain suspected terrorists, eavesdrop on communications and counter money-laundering. In November, President Bush signs a directive to try suspected terrorists in military tribunals rather than the courts.
2001 December - Energy giant Enron declared bankrupt after massive false-accounting comes to light.
2002 January - State of the Union address: President George W Bush includes Iraq, Iran and North Korea in what he describes as an "axis of evil".
2002 June/July - Telecoms giant WorldCom's multi-billion dollar accounting fraud is revealed, eclipsing the Enron scandal to become the biggest business failure in US history.
2002 November - President Bush signs into law a bill creating a Department of Homeland Security, the biggest reorganization of federal government in more than 50 years. The large and powerful department is tasked with protecting the US against terrorist attacks.
2003 February - Space shuttle Columbia's 28th mission ends in tragedy when the craft breaks-up while re-entering the atmosphere. The seven astronauts on board are killed.
2003 20 March - Missile attacks on targets in Baghdad mark the start of a US-led campaign to topple the Iraqi leader Saddam Hussein. US forces advance into central Baghdad in early April.
2003 1 May - Speaking on the deck of the aircraft carrier Abraham Lincoln, President Bush declares that the main part of the war in Iraq is over.
2003 14 August - Biggest power blackout in North American history hits cities in the north and east, including New York, as well as Canadian cities.
2004 May - Furor over pictures showing the abuse of Iraqi prisoners in US custody. President Bush and Defense Secretary Rumsfeld - who is questioned by Congress about the scandal - apologize for the mistreatment.
2004 June - Former President Ronald Reagan dies aged 93. He is accorded a state funeral.
2004 July - Senate report says US and allies went to war in Iraq on "flawed" information. Independent report into 11 September 2001 attacks highlights deep institutional failings in intelligence services and government.
Bush second term
2004 2 November - Presidential elections: George W Bush wins a second term. He is inaugurated on 20 January 2005.
2005 July - Space shuttle Discovery completes the first manned NASA space mission since the Columbia accident in February 2003.
2005 August - Hundreds of people are killed when Hurricane Katrina, the most destructive storm to hit the US in decades, sweeps through gulf coast states. Much of the city of New Orleans is submerged by flood waters.
2006 March - Congress renews the USA Patriot Act, a centerpiece of the government's fight against terrorism, after months of debate about its impact on civil liberties. The government agrees to some curbs on information gathering.
2006 April-May - Millions of immigrants and their supporters take to the streets to protest against plans to criminalize illegal immigrants.
2006 May - The only man to be charged over the September 11 attacks, self-confessed al-Qaeda conspirator Zacarias Moussaoui, is sentenced to life in jail.
2006 November - Democratic Party wins control of the Senate and House of Representatives in mid-term elections. Defense Secretary Donald Rumsfeld steps down.
2006 December - Former President Gerald Ford, who succeeded Richard Nixon in 1974, dies aged 93.
2007 January - President Bush announces a new Iraq strategy; thousands more US troops will be dispatched to shore up security in Baghdad.
2007 May - Congress approve more funding for the war in Iraq; President Bush had vetoed an earlier bill containing a timetable for withdrawal.
2008 January - Campaigning gets under way in earnest for the presidential elections in November, with both main parties - Republicans and Democrats - gearing up to choose their candidate.
2008 March - John McCain wins the Republican Party's nomination to run for US president.
2008 June - Illinois senator Barack Obama wins the Democratic Party's nomination to run for US president, becoming the first black candidate to do so, after defeating his rival Hillary Clinton.
2008 September - Turmoil in the US and international financial markets as major Wall Street investment bank Lehman Brothers collapses and other big US financial players face growing troubles as a result of the "credit crunch". With hundreds of billions of dollars wiped out in bad loans and a prolonged property slump, the US faces its worst financial crisis since the Great Depression.
The US House of Representatives rejects a $700bn rescue plan for the US financial system, sending shockwaves around the world.
2008 October - With the financial crisis spreading globally, the US Congress passes the previously rejected financial rescue plan.
2008 November - Democratic Senator Barack Obama defeats Republican John McCain to become the first black president of the United States.
Leaders from twenty of the world's biggest economies - the G20 - meet in Washington to discuss the deepening financial crisis and agree to cooperate more closely to stimulate worldwide economic growth.
The US Federal Reserve announces it will inject another $800bn into the economy in a further effort to stabilize the financial system and encourage lending.
2009 January - President-elect Barack Obama puts forward an $825 billion stimulus package for the ailing US economy. Congressional leaders say they intend to pass the bill by the middle of February.
Barack Obama sworn in as 44th president of the United States.