The National Space Society has an informative article on the history of the L5 society. The L5 society was started by Gerard K. O'Neill and others with the intention to put human space colonies at L5. L5 and L4 are spots in earth orbit that a mass can orbit indefinitely without expending energy. The L5 society envisioned space colonies that were large bio-sphere's, spinning in order to create an artificial gravity. The space colonies would have provided solar power to earth, among other economic activities. NSF funding for research projects, most notably the Solar Power Satellite project, stopped in 1981.