What agencies created airfields across america?

As the nation's air transportation system grew, so did the need for better aviation facilities. By 1940 the modern airport had come into being.

Aerodrome, landing field, air field: all described places an airplane could take off or land more than once. But open fields and parade grounds were unsuitable for commercial aviation. Without a network of adequate airports, an air transportation system was not possible.

As aircraft became bigger and passenger numbers rose, airports evolved to keep up. Air fields grew larger, grass gave way to pavement, and terminal buildings evolved from simple structures to architectural statements of modernity.

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hello,

the steamboat is your answer.

it seems like its the only form of transportation on the choices.