The Thumb is a region and a peninsula of the U.S. state of Michigan, so named because the Lower Peninsula is shaped like a mitten. The Thumb area is generally considered to be in the Central Michigan region, east of the Tri-Cities and north of Metro Detroit. The region is also branded as the Blue Water Area. The counties that constitute the Thumb form the peninsula that stretches northward into Lake Huron and Saginaw Bay. There is no formal list of which counties are part of the Thumb, but virtually all definitions include Huron, Tuscola, and Sanilac Counties, and most include Lapeer and St. Clair Counties. Economy The Thumb region is very flat with fertile soil, the reason for its historical role as a chiefly agricultural area. Major agricultural products include sugar beets, navy beans, corn, fruits, and fish from the Saginaw Bay and Lake Huron. Manufacturing—particularly concerning the automotive industry—is also prevalent in Michigan's Thumb due to the region's proximity to the automotive centers of Detroit and Flint. Industry The Thumb has many notable businesses, many linked to agriculture. Intertape Polymer Group, Inc. has a major factory in Marysville. Cargill Salt operates a large salt mine and factory in St. Clair. This is the only plant in the U.S.A. that produces Alberger salt, which is especially prized in the fast food industry because of its higher volume (due to its unique shape) and lower sodium content (for a given volume, not weight). This is part of Michigan's large salt-mining industry. Cooperative Elevator Company has been named the top Michigan Agriculture Exporter by the Michigan Department of Agriculture. Its headquarters are in Pigeon, and it has branch elevators in Deckerville, Akron, Gagetown, Sebewaing, Elkton, and Bad Axe. Detroit Edison is the operator of three power plants in the Thumb area: St. Clair and Belle River Power Plants in East China Township, and Greenwood Energy Center in Greenwood Township. Dow AgroSciences Harbor Beach manufactures agricultural chemicals: weed killer, fungicides, fertilizers and plant nutrients and herbicides. Mueller Industries owns and operates Mueller Brass in Port Huron. Grand Trunk Western Railway has a major rail yard in Port Huron Township. Marysville Hydrocarbons is an ethanol plant in Marysville. SMR Automotive manufactures rear view mirrors at facilities in Port Huron and Marysville. Port Huron-based P.J. Wallbank Spring manufactures components for transmissions. Port Huron's industrial park is home to many companies that produce plastic components