Complex sentence: Ross was a bicycle brand that manufactured over 15 million bicycles in the United States between 1946 and 1988--headquartered in Rockaway Beach, Queens, with manufacturing in Allentown, Pennsylvania.
Split into simpler sentences: Ross was a bicycle brand that manufactured over 15 million bicycles in the United States between 1946 and 1988. Its headquarters were in Rockaway Beach, Queens, and manufacturing was in Allentown, Pennsylvania.