There were a number of times in the history of the United States when German was dang close to, and before the Revolution may have even surpassed, English as far as the number of speakers.
While it's a legend that German was at one time considered for the official language of the United States and was defeated by a single vote, what is true is that in 1795 US laws and official documents were, for the first time, printed in a language alternate to English at the request of Germans living in the United States.
Up until around the Civil War, German was the predominant language in Pennsylvania.