It is well-known that Leigh Mercer published his immortal "A man, a plan, a canal--Panama!" in the November 13 1948 issue of Notes and Queries. But was his the first discovery? I feel it unlikely that this palindrome remained undiscovered until such a relatively late date. My feelings is based on the following considerations.
"Who First Found The Panama Palindrome?,"
Word Ways: Vol. 32
, Article 23.
Available at: https://digitalcommons.butler.edu/wordways/vol32/iss3/23