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@Phillyhistory, yup in the first paragraph I mention that the iconic yell did not appear for another 14 years. I can't say for sure, but my guess is that auditory sound is what helped propel the character to the pop cultural stratosphere.

This graph generated at Google Ngram suggests that the silent Tarzan, introduced in 1918, had a sharply declining reputation in the 1920s. But when the yell came out in the early '30s, well, that changed everything.

Tarzan ngram.JPG