 As the original SportsChannel was growing in popularity in New York City, Cablevision (through its then-broadcasting unit, Rainbow Media) eventually decided to form a new group of regional sports networks under the SportsChannel brand, with SportsChannel New York serving as the flagship charter affiliate.The expansion began with Cablevision's purchase of PRISM New England, a Boston-based premium channel previously owned by Spectacor, which was rechristened as SportsChannel New England on January 1, 1983.Other SportsChannel networks launched between 1984 and 1990 in markets such as San Francisco, Chicago, Philadelphia and Los Angeles.