In 1851 Guenther built the only grist mill in the German community of Fredericksburg, Texas. Eight years later he built a new mill in nearby San Antonio and put down roots. His legacy continues through C. H. Guenther & Son, Inc., a San Antonio-based food products company. It is the oldest business in Texas and the oldest continuously-operating family-owned milling company in the United States.
The first letters to and from Guenther's family in Germany were written at the time of his departure from Germany in 1848. They continue through the travails of getting established on the Texas frontier, then on through the Civil War to his only return visit to Germany, in 1891. They were translated from German by Regina Beckmann Hurst and by Walter D. Kamphoefner, Texas A&M University professor of history, who also contributed the foreword.