Levi’s original blue jeans were designated by style number 501.
The number appeared in 1890, when Levi Strauss & Co. began assigning lot numbers to its products. “501” was chosen for the company’s famous copper-riveted waist overalls, the garment that became the foundation of the modern Levi’s jeans line.
The jeans’ construction goes back to 1873, when Levi Strauss and tailor Jacob Davis received a U.S. patent for reinforcing workwear with metal rivets at points of strain. The original garment was called “waist overalls,” not jeans, and was made for demanding manual work.
A common mix-up is assuming the number identifies the year the jeans were invented. It does not: 1873 is the patent year, while 501 is the product’s lot or style designation. The company lost much of its early documentation in the 1906 San Francisco earthquake, so the specific reason for choosing 501 is not known. The style later became an enduring symbol of American denim.