Complex sentence: However, by September, Day had arranged the use of a polo field just north of Central Park bounded by 5th & 6th Avenues and 110th & 112th Streets in Manhattan that became known as the Polo Grounds, the first professional baseball park in Manhattan.
Split into simpler sentences: However, by September, Day had arranged the use of a polo field just north of Central Park in Manhattan, bounded by 5th & 6th Avenues and 110th & 112th Streets. The site became known as the Polo Grounds, the first professional baseball park in Manhattan.