Answer:
The Wyoming Territory was formed by the Organic Act on July 25, 1868, however, the area was part of many other territories and belonged to several other countries. Based on that date, Wyoming would be 143 years old as of July 25, 2011.
The first portion of the Wyoming Territory was part of the Louisiana Purchase in 1803, so, based on 1803, Wyoming would be 208 years old in 2011.