The Walt Whitman Archive has a 36-second recording taken from an old wax cylinder of what is thought to be Whitman himself reading four lines from his poem, America.
Here’s the text of the poem:
Centre of equal daughters, equal sons,
All, all alike endear’d, grown, ungrown, young or old,
Strong, ample, fair, enduring, capable, rich,
Perennial with the Earth, with Freedom, Law and Love,
A grand, sane, towering, seated Mother,
Chair’d in the adamant of Time.