1921
Reza Khan, a military officer in Persia's Cossack Brigade, names himself shah of Persia after successfully staging a coup against the government of the Qajar Dynasty. He immediately launches an ambitious campaign to modernize the country. Among other plans, he hopes to develop a national public education system, build a national railroad system and improve health care.

1925
Ahmad Shah, the Qajar dynasty's final ruler, is deposed, and an assembly votes in Reza Khan (who had adopted the last name Pahlavi) as Persia's new shah.

1926
Reza Khan Pahlavi is crowned, marking the beginning of the Pahlavi Dynasty. The shah's eldest son, Mohammad Reza, is named crown prince.

1935
Persia is officially renamed Iran. By the mid-'30s, Reza Khan's dictatorial approach begins to cause dissent.

1941
Although Reza Khan declares Iran a neutral power during World War II, Iran's British-controlled oil interests are largely maintained by German engineers and technicians, and Khan refuses to expel German citizens despite a request by Britain. In September 1941, following British and Soviet occupation of western Iran, Reza Shah is forced out of power. His son, Mohammad Reza Shah Pahlavi, succeeds him on the throne.

1949
An attempt on the shah's life, attributed to the pro-Soviet Tudeh Party, results in an expansion of the Mohammad Reza Shah Pahlavi's constitutional powers.

1951
Nationalist Prime Minister Mohammed Mossadeq attempts to nationalize the British-owned oil industry. The shah opposes Mossadeq and removes him from power, but he regains power and the shah leaves Iran.

1953
The shah returns to Iran when Gen. Fazlollah Zahedi -- with backing from the Central Intelligence Agency -- overthrows Mossadeq in an August coup d'etat.

1957
According to the Federation of American Scientists, U.S. and Israeli intelligence officers work with Iran to set up SAVAK, an Iranian intelligence organization later blamed for the torture and execution of thousands of political prisoners and violent suppression of dissent.

1963
The shah implements "The White Revolution," an aggressive campaign of social and economic Westernization that is met with intense popular opposition. Popular nationalist Ayatollah Khomeini is arrested in one of many crackdowns on the shah's opponents. By the late 1960s the shah relies regularly on SAVAK to quell dissidence.

1976
In one of a series of reforms that alienate his people, the shah replaces the Islamic calendar with an "imperial" calendar, beginning with the founding of the Persian Empire. Many of the shah's growing number of critics see this as anti-Islamic.

1978
Iranians resort to rioting, mass demonstrations and strikes to protest the shah's authoritarian rule. In response, he enforces martial law.

1979
January 16
The shah flees Iran amid intensifying unrest.

February 1
Islamic nationalist Ayatollah Khomeini returns from France, where he was exiled for his opposition to the shah's regime. He encourages the brewing revolution.

April 1
Under Ayatollah Khomeini's guidance, Iran declares itself a theocratic republic guided by Islamic principles, and a referendum is held to name it the Islamic Republic of Iran.

November 4
Islamic students storm the U.S. embassy in Tehran, taking hostage 52 American employees and demand that the shah return from receiving medical treatment in the United States to face trial in Iran. Ayatollah Khomeini applauds their actions. The hostage situation ignites a crisis between the United States and Iran.

1980
April
Iran and the United States sever diplomatic ties over the hostage crisis, and the U.S. embassy becomes a training ground for the Revolutionary Guards Corps.

July
The shah dies in exile in Egypt.

September
Iraq invades Iran after years of disagreements over territory, most notably the Shatt al Arab waterway. When Iraqi President Saddam Hussein announces his intention to reclaim the Shatt al Arab, an eight-year war breaks out.

1981
Following negotiations mediated by Algeria, the U.S. hostages are released after 444 days of captivity.

1985
The United States covertly seeks to sell arms to Iran in exchange for the release of seven American hostages being held by Iranian-backed militants in Lebanon, prompting the Iran-Contra scandal.

1988
July
An American navy ship, the USS Vincennes, shoots down an Iranian civilian plane, killing all 290 passengers and the crew. The United States later apologizes and agrees to financial compensation for the victims families, saying the civilian plane was mistaken for an attacking military jet.

August
Iran accepts United Nations Security Council Resolution 598, leading to a cease-fire in the Iran-Iraq War.

1989
February
Indian author Salman Rushdie’s book "The Satanic Verses" causes uproar among fundamentalist Muslims, and Ayatollah Khomeini places a fatwa (religious edict) on the writer, saying his book is "blasphemous against Islam." The ayatollah calls on all "zealous Muslims" to kill Rushdie, placing a $3 million bounty on his head.

June
Khomeini dies. An elected body of senior clerics -- the Assembly of Experts -- chooses the outgoing president of the Islamic Republic, Ali Khamenei, to succeed Khomeini as the national religious leader.

August
Ali Akbar Hashemi-Rafsanjani, the speaker of the National Assembly, becomes president. Rafsanjani was an influential member of the Council of Revolution of Iran in the Islamic Republic’s early days.

1993
Rafsanjani wins reelection.

1995
The United States places oil and trade sanctions on Iran, accusing the country of sponsoring terrorism, committing human rights abuses and seeking to sabotage the Arab-Israeli peace process.

1997
(Ali) Mohammad Khatami-Ardakani is elected to the presidency in a landslide victory amidst his pledges of political and social reforms as well as economic revitalization.

2001
President Khatami wins reelection.

2000
Pro-reform candidates and allies of President Khatami win 189 of the 290 seats in parliament, setting the stage for reformers to control the legislature for the first time since the 1979 Islamic revolution. Conservatives win 54 seats, independents 42 and another five seats are reserved for religious minorities.

2002
In his January State of the Union speech, American President George W. Bush refers to Iran as part of an "axis of evil," saying the country is actively pursuing weapons of mass destruction. The speech is met with anger in Iran. Iranian Foreign Minister Kamal Kharrazi responds by calling President Bush's comments "arrogant" and saying Iran sees them as "interference in its internal affairs."

2003
The International Atomic Energy Agency says Iran admits to plutonium production, but the agency says there is no evidence that Iran is developing nuclear weapons. Iran agrees to more rigorous U.N. inspections of nuclear facilities.

-- By Jessica Moore, Online NewsHour