The first elephant to arrive in the USA was in 1796, and was exhibited around the country, so it was a question people asked — “Have you seen the elephant?”
In the mid 1800’s it was an idea often expressed in the West of America when someone was dying — “You’ve seen the elephant!”— meaning they’ve seen and experienced everything worthwhile in this world and it was now OK to die. http://www.awb.com/dailydose/?p=1097
