Timeline

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 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
September 14, 2015 During an engineering test a few days before the first official search begins, Advanced LIGO detects strong gravitational waves from collision of two black holes.
2016 January: First observing run of LIGO advanced detectors ends