Platte County, Wyoming courthouse built in 1918. Located in Wheatland, Wyoming. – courthousehistory.com, CC BY-SA 4.0 – Wikimedia Commons Platte County is located in Wyoming. About 8,605 people live here (as of 2020). Between 2010 and 2020, the population declined from 8,667 to 8,605. The area covers about 5,467.0 square kilometers. The region is divided into 5 Municipalities. The region was founded in 1913. The name originates from North Platte River (major tributary of the Platte River) Platte County is county in Wyoming, United States. More information at plattecountywyoming.com.