William R. Mensinger started American Lumber Company in 1923. He was a first generation American, his father immigrated to Iowa in 1850 from Schleswig. He came to California around 1900 and was impressed with its potential. He became a farmer, rancher, and real estate developer. He opened Modesto's first theatre. After it burnt down he opened Modesto's second theatre. This brick building still stands on Tenth Street in Modesto.
American Lumber Company was built at 9th and M Street in downtown Modesto and remains at that location. In the 1970's American Lumber Company added a hardware store to its facilities. In the early 1990's American Lumber Company began selling high quality wood, windows, and patio doors from Andersen, Marvin, and Pozzi. The Company is also a certified dealer for Milgard Vinyl windows and has an extensive door and window showroom.
Since 1923 American Lumber Company has been owned and operated by members of the Mensinger family. The current President, John B. Mensinger is the grandson of William R. Mensinger, and has been working at American Lumber Company since 1986.