In the mid 1950s Levi Strauss & Co. started selling the 501® Jeans on America’s east coast for the first time (the western states had been the only sales territory since the jeans came out in 1873). Many folks had already been introduced to the jeans at dude ranches, but to some, this button fly work pant was something they had never encountered. In order to make potential consumers comfortable with the company’s products, LS&Co. introduced a zipper version of the button fly Shrink-To-Fit® jeans in 1954: the 501Z®.
It had everything long- time wearers loved: the silhouette, the tough but flexible fabrics, rivets, etc. Retailers carried both the 501® Jean and its zippered brother, the 501Z® Jeans, and everyone got the pair that worked best for them. The 501Z® Jeans had many fans. It was given the new number 502 in 1967 and remained in the line until 1976, when the pre- shrunk jean surpassed it in popularity.