Work boots and shoes that are famed for their comfort and durability have been made in Red Wing, Minnesota since 1905. The full-grain cow hide used to make Red Wings are treated according to a special technique that was developed at the end of the 1940s and patented for Red Wing: The company purchases hides that have been pre-processed with chromium salts and then tans them using mineral oil, hence the term "oil-tanned". This gives the leather an oil content of 22% (8 to 10% is normal), which makes it exceptionally flexible, hard-wearing and water-repellent despite its thickness. The quality of the workmanship corresponds to the high quality of the leather. Red Wing shoes are mechanically welted using the complex Goodyear welt technique.