Does this sentence begin with a prepositional phrase:

Across the fence the ball soared, and that's when you gave me the Wagner baseball card. Thanks

Yes

Thank you.

Yes, the sentence "Across the fence the ball soared, and that's when you gave me the Wagner baseball card" begins with a prepositional phrase.

A prepositional phrase starts with a preposition (in this case, "Across") and ends with a noun or pronoun (in this case, "fence"). In this sentence, "Across the fence" is the prepositional phrase that indicates the location or direction of the ball soaring. It sets the stage for the action happening in the rest of the sentence.