Complex sentence: The "Rachel" remains one of the most popular hairstyles in history, and was the most popular hairstyle in the United States since actress Farrah Fawcett's "Charlie's Angels" hairstyle.
Split into simpler sentences: The "Rachel" remains one of the most popular hairstyles in history. Additionally, it was the most popular hairstyle in the United States since actress Farrah Fawcett's "Charlie's Angels" hairstyle.