Complex sentence: The National Historical Park was authorized on October 71988 (U.S. public law 100-479; H.R.4457), and the William Johnson House was added to it on September 28 1990 (U.S. public law 101-379; H.R.4501).
Split into simpler sentences: The National Historical Park was authorized on October 71988 (U.S. public law 100-479; H.R.4457). The William Johnson House was added to it on September 28 1990 (U.S. public law 101-379; H.R.4501).