Hispanic Heritage Month began in September 1968 when Congress authorized President Lyndon B. Johnson to celebrate National Hispanic Heritage Week. In 1989, Congress extended the celebration to a month, September 15 through October 15, in recognition of the independence of five Latin American countries: Costa Rica, El Salvador, Guatemala, Honduras, and Nicaragua. Mexico, Chile, and Belize also celebrate their indepedence days during this period as well as Columbus Day. More information here.
The term Hispanic or Latino, as defined by the U.S. Census Bureau in 2010, refers to Puerto Rican, South or Central American or other Spanish culture or origin regardless of race. According to the 2010 Census, there are 50.5 million people of Hispanic or Latino origin. Hispanics represent 16% of the population. Read more here.