1787 The Constitution of the United States is drafted and signed; Federalist Papers are published

1789 Constitution is ratified; George Washington is elected as first president; Judiciary Act passes

1791 Bill of Rights is adopted

1794 Whiskey Rebellion is put down

1795 Eleventh Amendment, prohibiting lawsuits against states in federal court, is ratified

1798 Alien and Sedition Acts are passed

1800 Capital moves from Philadelphia to Washington, D.C.

1803 Thomas Jefferson approves Louisiana Purchase, doubling the size of the United States; Supreme Court establishes doctrine of judicial review

1804 Lewis and Clark begin exploration of the Northwest Territories

1804 The Twelfth Amendment, altering presidential elections, is ratified

1808 Slave trade is banned

1810 United States annexes west Florida

1814 During the War of 1812 with England, Francis Scott Key writes the words to “The Star-Spangled Banner”; Treaty of Ghent is signed, ending the war of 1812

1817 New York Stock Exchange is founded

1819 Spain cedes Florida to the United States

1820 Missouri Compromise outlaws slavery in states north of latitude 36° 30'

1823 President James Monroe warns European countries not to interfere in the diplomacy of the Western Hemisphere, establishing the Monroe Doctrine

1830 President Jackson signs the Indian Removal Act, forcing all Native Americans to move west of the Mississippi

1841 President William Henry Harrison is inaugurated on March 4, and dies from pneumonia on April 4, having served what today is still the shortest presidential term in American history

1848 United States accepts Republic of Texas into the Union after winning Mexican-American War

1849 California gold rush gets underway

1854 Kansas-Nebraska act is signed, admitting the two states to the Union and repealing the Missouri Compromise; Republican Party is formed

1857 In the Dred Scott case, the Supreme Court rules that Congress cannot ban slavery and that slaves aren't citizens

1860 Abraham Lincoln is elected president

1861 Civil War begins when Confederacy attacks Ft. Sumter in South Carolina

1863 President Lincoln signs the Emancipation Proclamation, freeing the Southern slaves; delivers Gettysburg Address

1865 Civil War ends; President Lincoln is assassinated by John Wilkes Booth; Thirteenth Amendment, prohibiting slavery, is ratified

1867 United States purchases Alaska from Russia

1868 Fourteenth Amendment is ratified, creating due process and equal protection of the law for all Americans; President Andrew Johnson is impeached by the House and acquitted by one vote in the Senate

1869 Transcontinental railroad is completed

1870 Fifteenth Amendment gives all male Americans the right to vote

1878 President Rutherford B. Hayes installs first telephone in the White House

1883 Pendleton Act establishes federal civil service

1886 American Federation of Labor (AFL) is organized

1890 Sherman Anti-Trust Act is passed

1896 In Plessy v. Ferguson, Supreme Court declares that segregation is legal so long as it's “separate but equal,” paving the way for Jim Crow in the South

1898 United States annexes Hawaii

1901 Following the assassination of William McKinley, Theodore Roosevelt becomes president

1909 NAACP is formed

1913 Federal Reserve system is created; Sixteenth Amendment gives Congress the right to levy an income tax; Seventeenth Amendment puts into effect the direct election of U.S. senators

1914 Panama Canal opens, linking the Atlantic and Pacific oceans

1917 United States enters World War I

1919 Eighteenth Amendment prohibits the consumption of alcohol; Senate rejects the Treaty of Versailles

1920 Nineteenth Amendment gives women the right to vote

1929 Stock market crashes; beginning of Great Depression

1933 Franklin Roosevelt is inaugurated as president; Twentieth Amendment moves the presidential inauguration date from March 4 to January 20; Twenty-first Amendment repeals prohibition

1935 Social Security Act is passed

1937 President Roosevelt's plan to “pack” the Supreme Court is rebuffed by Congress

1941 Japan attacks Pearl Harbor; United States enters World War II

1944 D-Day liberation of Western Europe

1945 Allied forces defeat Germany; atomic bombs are dropped on Hiroshima and Nagasaki; Japan surrenders; United Nations is established

1948 Congress passes the Marshall Plan to rebuild Western Europe; Truman Doctrine of “containing” communism is established

1949 North American Treaty Organization (NATO) is created; Soviet Union acquires atomic bomb

1950 United States enters Korean War

1951 Twenty-second Amendment limits president's tenure to two terms

1953 Korean War ends

1954 Supreme Court outlaws school segregation in Brown v. Board of Education; Wisconsin Senator Joseph McCarthy is censured by the Senate

1959 Hawaii and Alaska become the last two states to join the United States

1961 Twenty-third Amendment gives residents of the District of Columbia the right to vote in presidential elections

1963 President John F. Kennedy is assassinated

1964 Congress authorizes use of force in Vietnam; Civil Rights Act is passed; Twentyfourth Amendment eliminates poll taxes as an obstacle to voting

1965 Medicare is established as part of Lyndon Johnson's Great Society program

1967 Thurgood Marshall is appointed first African-American justice to the Supreme Court; Twenty-fifth Amendment outlines presidential and vice presidential succession

1968 Martin Luther King Jr. is assassinated

1969 Neil Armstrong and Edwin (Buzz) Aldrin Jr. walk on the moon

1971 Twenty-sixth Amendment gives eighteen-year-olds the right to vote

1973 War Powers Act is passed; Supreme Court legalizes abortion in Roe v. Wade

1974 President Nixon is impeached and resigns from office

1981 U.S. hostages in Iran are released after 444 days in captivity; Sandra Day O'Connor becomes first woman Supreme Court justice

1986 President Reagan overhauls federal tax code

1989 End of the cold war

1990 Americans with Disabilities Act is passed

1992 Twenty-seventh Amendment alters the process for congressional pay raises

1994 NAFTA agreement is passed

1996 President Clinton signs welfare reform legislation

1998 President Clinton is impeached by the House of Representatives and acquitted the following year

2001 Terrorist attacks on the World Trade Towers and Pentagon kill over 3,000 people

2002 Department of Homeland Security created