Simplify the following text for a Grade 5 native English-speaking person.
Original: U.S. Route 66 ( also known as the Will Rogers Highway after the humorist , and colloquially known as the `` Main Street of America '' or the `` Mother Road '' ) was a highway within the U.S. Highway System .
Simplified: U.S. Route 66 ( also known as Route 66 , U.S. Highway 66 , The Main Street of America , The Mother Road and the Will Rogers Highway ) was a highway in the U.S. Highway System .