Complex sentence: New York State Route 23A (NY 23A) runs east--west across Greene County as an alternate route of NY 23 in the northern Catskill Mountains.
Split into simpler sentences: New York State Route 23A (NY 23A) is an east--west state highway in Greene County, New York, in the United States. It serves as a alternate route of NY 23 through the northern Catskill Mountains.