Many things happened in the 20th century that were successful and beneficial to the growth of America. Things like economic, urban, social and political improvements, along with the expansion of civil rights and liberties and the growth of the United States into a global superpower. Since 1913 the population has grown from 1.8 billion Americans to 2.5 billion in 1950, which is a huge increase in social growth. Along with the increase in population, food production also increased; Farmers built more irrigation systems to supply water to the land and strengthen urban life. Many people in the early 20th century began to move to cities. The percentage of the world's urban population living in towns and cities has increased from 18% to nearly 30%. In the 1950s, more than 50% of people in industrialized countries lived in cities. In 1904, Theodore Roosevelt provided the Roosevelt Corollary which affirmed America's right to intervene in the economic affairs of South America, Central America, and the Caribbean. This was successful because it was used to secure future US military interventions in many countries. Then, William Howard Taft became the 27th president on March 4, 1909 and faced the Great War a few years later. On June 28, 1914, Austrian Archduke Franz Ferdinand was assassinated in Austro-Hungary, starting the First World War. Austria-Hungary then attacked Serbia; both sides had treaties with other countries, which formed the Allies and the Central Powers. The allies were France, the United Kingdom and Russia while the Central Powers were Germany and Austria-Hungary. The allies needed help and hoped America would help and join them. But America did not want to get involved in a war so far away that did not afflict...... half of the document ......Lecture, History since 1865 from Rowan University, Glassboro, NJ, February 25, 2014.Harris , Skylar. "The new deal." Rowan University Lecture, History since 1865, Glassboro, NJ, March 11, 2014.Harris, Skylar. “The Progressive Era.” Rowan University Lecture, History Since 1865, Glassboro, NJ, February 18, 2014. Harris, Skylar . "The Roaring '20s and the Great Depression." Rowan University Lecture, History Since 1865, Glassboro, NJ, February 27, 2014."WalterCoffey.com." WalterCoffeycom. http://waltercoffey.wordpress.com/tag/roosevelt-corollary/ (accessed April 15, 2014).A&E Television Networks. "Second World War." History.com. http://www.history.com/topics/world-war-ii (accessed 12 April 2014). BBC. "World War II: Summary Outline of Key Events". BBC News. http://www.bbc.co.uk/history/worldwars/wwtwo/ww2_summary_01.shtml (accessed April 15, 2014).