Complex sentence: It was placed on the National Register of Historic Places in 1977, and in 1991 the Coast Guard leased the lighthouse to the city of Mukilteo, although navigational equipment is still maintained by the Coast Guard.
Split into simpler sentences: It was placed on the National Register of Historic Places in 1977. In 1991, the Coast Guard leased the lighthouse to the city of Mukilteo, although navigational equipment is still maintained by the Coast Guard.