do i need a visa to be able to visit the great wall on china during a long layover

Hi. I purchase a ticket to travel to tokyo, Japan from USA, California. I have a 11hr layover in PEK Beijing Capital Apt China. I'll be arriving at 5:20 and departing to Japan at 4:40pm. I wanted to see the great wall and I wanted to know if I need to apply since I'm a citizen of the USA I think I qualify for free. If I do please let me know what do I need to do to be able to leave the airport and come back to catch my flight. Thank you