Faith whose oldest standing temple is in Wilmette, Illinois (5)

I believe the answer is:

bahai

(Other definitions for bahai that I've seen before include "Religious follower" , "Religion of peace/unity" , "Religion founded in the 19th-century" , "Religion originating in 19th century Iran" , "Religion emphasising unity and peace" .)

I've seen this clue in the LA Times.

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