Today I got an interesting cover from the USA! The cover was sent from the city of Mercury, which is located in the state of Nevada. Mercury is a part of Nye County and is located 65 miles from Las Vegas. Interestingly, the city is currently the only closed city in the USA. This means that the city is not accessible to the general public. This is because Mercury is located within the Nevada Test Site. It was built to house the staff of the test site. It is currently governed by the US Department of Energy and an estimated 500 people live in the city. An interesting red postmark was used and it was also later hand cancelled at Las Vegas.