A physics research facility developed to detect cosmic gravitational waves and to measure these waves for scientific research. It consists of two installations within the continental United States, located in the states of Washington and Louisiana, operated in unison as a single observatory. Funded by the National Science Foundation (NSF), LIGO was designed and constructed by a team of scientists from the California Institute of Technology and the Massachusetts Institute of Technology, and by industrial contractors. Construction of the facilities was completed in 1999, and operation of the detectors began in 2001. LIGO is the leading member in a developing global network of gravitational-wave observatories.