The Old Mill has been awarded the coveted National Register of Historic Places designation by the Federal Department of the Interior. This award was issued not only for the age of the original building (1924), but also due to its unique construction as one of the first poured in place solid concrete buildings in central Texas.

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The facility was also recognized as having housed the largest wool scouring mill west of the Mississippi operating until 1985. In 1988, the abandoned buildings, which were most likely going to be leveled, were purchased and gradually turned into the Old Mill Business Park, one of the largest business complexes in Hays County.

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A historical anthology from 1924 to 1985 is on file in the San Marcos Public Library.