What were the economic and social condition of America in the early 1900s (1900-1940)?

http://www.theusaonline.com/history/industrialization.htm

http://www.encyclopedia.com/doc/1G2-3468300036.html

http://www.nebraskastudies.org/0700/frameset_reset.html?http://www.nebraskastudies.org/0700/stories/0701_0105.html

http://www.econlib.org/library/Enc1/WagesandWorkingConditions.html