the east, such as the 2nd Wisconsin Volunteer Infantry Regiment, 6th Wisconsin Volunteer Infantry Regiment, and 7th Wisconsin Volunteer Infantry Regiment, which formed part of the Iron Brigade. These three regiments fought in the Northern Virginia Campaign, the Maryland Campaign, the Battle of Fredericksburg, the Battle of Chancellorsville, the Gettysburg Campaign, the Battle of Mine Run, the Overland Campaign, the Siege of Petersburg, and the Appomattox Campaign. The 8th Wisconsin Volunteer Infantry Regiment, which fought in the western theater of war, is also worthy of mention, having fought at the Battle of Iuka, the Siege of Vicksburg, the Red River Campaign, and the Battle of Nashville. The 8th Wisconsin is also known for its mascot, Old Abe. Economic growth Agriculture Agriculture was a major component of the Wisconsin economy during the 19th century. Wheat was a primary crop on early Wisconsin farms. In fact, during the mid 19th century, Wisconsin produced about one sixth of the wheat grown in the United States. However, wheat rapidly depleted nutrients in the soil, especially nitrogen, and was vulnerable to insects, bad weather, and wheat leaf rust. In the 1860s, chinch bugs arrived in Wisconsin and damaged wheat across the state. As the soil lost its quality and prices dropped, the practice of wheat farming moved west into Iowa and Minnesota. Some Wisconsin farmers responded by experimenting with crop rotation and other methods to restore the soil's fertility, but a larger number turned to alternatives to wheat. In parts of northern Wisconsin, farmers cultivated cranberries and in a few counties in south central Wisconsin, farmers had success growing tobacco, but the most popular replacement for wheat was dairy farming. As wheat fell out of favor, many Wisconsin farmers started raising dairy cattle and growing feed crops, which were better suited to Wisconsin's climate and soil. One reason for the popularity of dairy farming was that many of Wisconsin's farmers had come to the state from New York, the leading producer of dairy products at the time. In addition, many immigrants from Europe brought an extensive knowledge of cheese making. Dairying was also promoted by the University of Wisconsin–Madison's school of agriculture, which offered education to dairy farmers and researched ways to produce better dairy products. The first test of butterfat content in milk was developed at the university, which allowed for consistency in the quality of butter and cheese. By 1899, over ninety percent