This image was acquired from
wikimedia. It was marked as Public Domain or CC0 and is free to use. To verify, go to the source and check the information there.
Keywords from Image Description:
First Transcontinental US Air Mail under Contract . Cover carried from San Francisco to Chicago on the first Transcontinental US Air Mail under Contract July PDUSGov Original upload log page en FirstTranscontinentalUSAirMailunderContract Centpacrr bytes no carried from San Francisco to Chicago on the first Transcontinental