Complex sentence: The lighthouse once was run by United States Coast Guard, but in 1976 an automatic light was installed, and since 1994 it has been staffed and maintained by the volunteer "New Dungeness Light Station Association".
Split into simpler sentences: The lighthouse once was run by United States Coast Guard, but in 1976 the agency installed an automatic light. Since 1994 the lighthouse has been staffed and maintained by the volunteer "New Dungeness Light Station Association".