- 1609 Henry Hudson explores the Hudson River.
- 1696 Caleb Heathcote purchases a large tract of land including what is now New Castle from Wampus and other Native American sachems.
- 1730 Quakers begin settling in the northern and western parts of North Castle, which will become New Castle.
- 1753-4 Quakers build meetinghouse on Quaker Road.
- 1776 Following the Battle of White Plains, the Quaker meetinghouse is used as a hospital for wounded soldiers of Washington's army.
- 1791 New Castle is divided from North Castle and becomes a separate town.
- 1846 The New York and Harlem Railroad, later the Harlem Division of the New York Central Railroad, reaches Chappaqua.
- 1853 Horace Greeley begins buying property in what is now downtown Chappaqua.
- 1872 Horace Greeley runs for president against incumbent Ulysses S. Grant.
- 1881 The New York and Northern Railroad, later the Putnam Division of the New York Central Railroad, reaches Merritt's Corners, now Millwood.
- 1902 Opening of the present Chappaqua railroad station, on property donated by Horace Greeley's daughter, Gabrielle Greeley Clendenin.
- 1904 A tornado sweeps across Quaker Road between the Sutton Reynolds house south of Gray Rock Lane and the Dodge house north of Marcourt Drive.
- 1912 The first central water system is installed in Chappaqua.
- 1914 Dedication of the Horace Greeley memorial statue.
- 1918 Dedication of Liberty Ship USS Chappaqua.
- 1929 Opening of the Horace Greeley School, now the Robert E. Bell Middle School.
- 1930 Celebration of the Chappaqua bicentennial. Opening of the railroad bridge.
- 1934 The Saw Mill River Parkway reaches Chappaqua.
- 1939 The Reader's Digest moves its headquarters to Chappaqua.
- 1957 Opening of the present Horace Greeley High School.
- 1958 Service ends on the Putnam Division of the New York Central Railroad.
- 1966 Founding of the New Castle Historical Society.
- 1999 President Bill Clinton and future Senator Hillary Rodham Clinton make their home in Chappaqua.
- 2000 Opening of the restored Horace Greeley House.