| 1970s |
Early work on gravitational-wave detection by laser interferometers, including a 1972 MIT study describing a kilometer-scale interferometer and estimates of its noise sources |
| 1979 |
U.S. National Science Foundation (NSF) funds Caltech and MIT for laser interferometer research and development |
| 1983 |
MIT and Caltech jointly present results of the kilometer-scale interferometer study to NSF. Receive NSF committee endorsement on new large programs in physics. |
| 1984 |
LIGO founded as a Caltech/MIT project. National Science Board approves LIGO development plan. |
| 1986 |
Physics Decadal Survey and special NSF panel on gravitational wave interferometers endorse LIGO |
| 1990 |
National Science Board (NSB) approves LIGO construction proposal, which envisions initial interferometers followed by advanced interferometers |
| 1992 |
NSF selects LIGO sites in Hanford, Washington, and Livingston, Louisiana. LIGO Cooperative Agreement signed by NSF and Caltech. |
| 1994-95 |
Site construction begins at Hanford and Livingston locations |
| 1997 |
The LIGO Scientific Collaboration (LSC) is established and expands LIGO beyond Caltech and MIT, including the British/German GWO Collaboration, which operates the GEO600 interferometer in Hannover, Germany. |
| 1999 |
LIGO inauguration ceremony |
| 2002 |
First coincident operation of Initial LIGO interferometers and the GEO600 interferometer |
| 2004 |
NSB approves Advanced LIGO |
| 2006 |
LIGO design sensitivity achieved. First gravitational wave search at design sensitivity. Science Education Center inaugurated at the LIGO Livingston Observatory. |
| 2007 |
Joint data analysis agreement ratified between LIGO and the Virgo Collaboration, which operates the Virgo interferometer in Cascina, Italy. Joint observations with enhanced initial LIGO interferometer and Virgo. |
| 2008 |
Construction of Advanced LIGO components begins |
| 2010 |
Initial LIGO operations conclude; Advanced LIGO installation begins at the observatories. |
| 2011 - 2014 |
Advanced LIGO installation and testing |
| 2014 |
Advanced LIGO installation complete |
| 2014-2015 |
Advanced LIGO sensitivity surpasses Initial LIGO |
| Sept 14, 2015 |
Advanced LIGO detects gravitational waves from collision of two black holes |
| Dec 26, 2015 |
LIGO observes a second binary black hole coalescence |
| Jan 12, 2016 |
First observing run of LIGO advanced detectors ends |
| Jan 4, 2017 |
LIGO observes its third binary black hole coalescence |
| Aug 14, 2017 |
Gravitational waves from a binary black hole merger observed by LIGO and Virgo |
| Aug 17, 2017 |
LIGO and Virgo make first detection of gravitational waves produced by colliding neutron stars |
| Aug 25, 2017 |
Second observing run of LIGO advanced detectors ends |
| Oct 3, 2017 |
LIGO co-founders Rainer Weiss, Barry Barish, and Kip Thorne are awarded the 2017 Nobel Prize in Physics |
| Apr 1, 2019 |
Third observing run of LIGO advanced detectors begins |
| May 2, 2019 |
LIGO and Virgo detect neutron star smash-ups |
| Oct 1 - 31, 2019 |
LIGO commissioning break |
| Nov 1, 2019 |
Third observing run of LIGO advanced detectors resumes |
| Jan 6, 2020 |
LIGO-Virgo Network Catches Another Neutron Star Collision |
| Mar 26, 2020 |
LIGO Suspends Third Observing Run (O3) due to COVID-19 |
| Jun 23, 2020 |
LIGO-Virgo Finds a Mystery Object in "Mass Gap" |
| May 24, 2023 |
Fourth observing run (O4) begins |
| March 19, 2025 |
LIGO reaches 200 gravitational wave detections in O4 |
| August 25, 2025 |
LIGO Founder and Champion, Rainer Weiss passes at age 93 |
