Adolph Kiefer, the swimming legend has passed away. He hailed from which country?

Q. Adolph Kiefer, the swimming legend has passed away. He hailed from which country?
Answer: United States
Notes: Adolph Gustav Kiefer (98), the oldest-living Olympic champion, has recently passed away in Wadsworth, Illinois. He was the first man in the world to swim 100-yard backstroke in under one minute. Kiefer was also an inventor and innovator of new products related to aquatics competition.