By Brad Segall

PHILADELPHIA (CBS) – A local historian from Bucks County has uncovered what may be the only recording from a speech Dr. Martin Luther King made in Philadelphia nearly half a century ago, and just months before he was murdered.

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It’s believed to be Dr. King’s only major speech in Philadelphia before an audience of more than 3,000 at the Alumni Field House on the campus of what was then called St. Joseph’s College.

Historian Tom Lingenfelter says the recording, and some unpublished photos, were found in the collection of a journalist who covered the 1967 event:

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“I think it’s really called ‘the quintessential speech’ in that it has just about every issue he was really concerned about.”

The hour-long speech features King crediting President Kennedy for having the courage to admit a mistake involving the Bay of Pigs and he reaches out to President Johnson.

“I think it’s time now for our president…for our secretary of state…for our secretary of defense to stand up before America and the world and honestly admit that we made a mistake in Vietnam,” Dr. King said in the speech.

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Lingenfelter says plans are being considered for its presentation to the public.