C. H. Guenther and Son, Incorporated, doing business as Pioneer Flour Mills, produces baking-mix products for the retail market in twenty-two states in the South and Southwest and for food-service companies that supply hotels, restaurants, and other public institutions throughout the nation. The company also markets gourmet mixes for biscuits, gravies, muffins, and pancakes under its San Antonio River Mill Store trade name to the direct-mail gift market and wholesale to specialty stores and frozen baked products from its Pioneer Frozen Foods subsidiary in Duncanville (near Dallas) throughout the United States. In the 1990s the firm employed over 600 workers. The White Lily Foods Company of Knoxville, Tennessee, a producer of flour, cornmeal, and baking mixes, became a wholly owned subsidiary in 1995.
The company was founded in 1851 nine miles west of Fredericksburg on the banks of Live Oak Creek by Carl Hilmar Guenther, a millwright who had been accepted into the guild of master millwrights in Europe in 1844. In 1859 Guenther purchased a mill site adjacent to the King William Historic District on the banks of the San Antonio River, which has been Pioneer headquarters ever since. Guenther moved to the United States from Weissenfels, Saxony, in 1848, and traveled across the country for three years looking for a place to settle. In 1851 he sailed into Indianola, Texas, and traveled to San Antonio and on to Fredericksburg, where he was struck by the lack of facilities to mill grains (wheat, corn, and rye) grown in the area. After his first mill was destroyed by flooding days before its completion, Guenther built a second mill that prospered over the next eight years, allowing him to consider expanding. Because of occasional floods and droughts along the Live Oak as well as the growth of San Antonio, he decided to build his next mill on a tract of land one mile south of that city. Unable to construct a mill alone, Guenther turned to a group of Alsatian immigrants who had begun to farm land southwest of San Antonio in Castro's Colony (now known as Castroville). By trading them milling for labor, he convinced them to help dig a channel and construct the buildings necessary to begin production. Initially, the mill became a meeting place for members of the German community. Guenther was an active participant, helping to form a club and build a clubhouse, or Vereins-Haus, and later employing many German workers. The mill operated using grain grown in and around San Antonio until 1876, when the arrival of the railroads first connected the city to the grain-growing areas of the Midwest. Guenther also established an ice plant known as the Southern Ice Company, which eventually became part of the city's Southern-Henke Ice Company.
In 1898 the milling business was incorporated under the name of C. H. Guenther and Son, Incorporated, using the trade name Pioneer Flour Mills. In 1902 Guenther retired from the mill and turned over its control to his youngest son, Erhard, who ran the mill until 1945. The mill introduced its first ready-mixed baking product in 1953, at which time a new plant to manufacture prepared mixes was completed. Adjacent to the main plant in San Antonio, the original Guenther family home, built in 1860, is open to the public. The restored home contains the River Mill Store, conference rooms, a museum, and a restaurant. The company is still controlled by Guenther's descendants, with eight of its ten board seats belonging to family members.