The modern era came about in part because of which historical event

Modern history, the modern period or the modern era, is the linear, global, historiographical approach to the time frame after post-classical history.  

Modern history can be broken down into periods:

•The early modern period began approximately in the early 16th century; notable historical milestones included the European Renaissance, the Age of Discovery, and the Protestant Reformation  

•The late modern period began approximately in the mid-18th century; notable historical milestones included the American Revolution, the French Revolution, the Industrial Revolution, the Great Divergence, and the Russian Revolution. It took all of human history up to 1804 for the world's population to reach 1 billion; the next billion came just over a century later, in 1927.  

•Contemporary history is the span of historic events from approximately 1945 that are immediately relevant to the present time.

b) race riots in several cities

on february 25, 2004, at the time the president of united states of america george bush announced that he supports the constitutional amendment to ban the same-sex marriage. but the possibility was left that states can decide whether they allow civil unions.