See other counties inMissouri. Platte County, Wyoming PO Box 728 Wheatland, WY 82201 Phone:(307) 322-3555 Fax:(307) 322-2245 In southeastern WY, north of Cheyenne; created Feb 9, 1911 from Laramie County.Name Origin:For the North Platte River, which flows through the county; French 'fla...