In 1964, Karl Birkenstock launches the Madrid Model (shown here). It was the first fitness sandal with a deep and flexible footbed.
Then in 1966, the Birkenstock Co. came to the U.S. market.
In 2016, Birkenstock celebrated 50 years in the United States. The company still thrives with customers each day.
In the early 1990's, there was a surge of popularity among high school & college aged generation Xers.
During the 2004 US presidential primary, some conversations derived Howard Dean's supporters as "Birkenstock Liberals".
In the US, it was first popular among young men & later on, flower children, a group associated with American Liberalism.