Automobiles and airplanes were made for transportation. Radios and movies came out as well, thus improving communication.
They used trains, cars, small trucks, and the horse and buggy. Commercial airline use, however, was not yet in existence.
1920 through 1929 was the 1920s. The year 1930 was the first year of the 1930s.
The roarin' 1920's were the opposite of the 1930's. The 1920's were a peak in the economy, wheras the 1930's were the time of the Great Depression.
http://www.scribd.com/doc/1768/Some-stories-about-popular-inventions-and-discoveries This is a good article describing a number of technological advances that led to things we use today. For example, the modern microphone was invented in 1920.
Besides the library, there are several websites where a person can find the 1920 and 1930 census. Some of the names of the websites are 1930 Census, Archives, and NYPL.
Institute of Transportation Engineers was created in 1930.
Armour Transportation Systems was created in 1930.
1920-1930
1920
about during 1920~1930
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1920-1930.