Another section was built the following year connecting Wilson to Grainfield. The first post office in Grainfield was established in May, 1879. Grainfield is served by USD 292 Wheatland. The Grainfield Opera House is listed on the National Register of Historic Places. Grainfield is located at (39.114101, -100.467540). The Grainfield Opera House, located at Main and 3rd Sts. Grainfield is a city in Gove County, Kansas, United States.