In 1854, the Kansas-Nebraska Act became law and decreed that the residents of the Kansas and Nebraska Territories could vote whether to enter the Union as free or slave states. In the immediate aftermath of the bill, large groups of both pro-slavery and anti-slavery settlers moved to the Kansas Territory. For the next 6 years, Kansas saw a variety of violent conflicts and political maneuvers over the issue. Eventually, Kansas entered the Union as a free state in January of 1861, three months before the Civil War started at Fort Sumter.

The doubling of the U.S. population from 1790 to 1820 was primarily the result of reproduction. It was not until after the early 1820s that immigration numbers began to dramatically increase.

During the 19th century, the Germans and the Irish were the largest immigrant populations in the United States. The Irish Potato Famine during the 1840s led to an increase in the already high Irish immigration numbers, and the 1848 revolutions in Germany led to an even greater increase in the already higher German immigration numbers. From 1840-1880 Germany supplied the greatest number of immigrants to the United States.

All four of these were social reform movements that began in the period before the American Civil War. Other reforms during the antebellum period include prison reforms, mental hospital reforms, education reforms, Protestant revivalism, and more.

The quote refers to the difficulty of American men to reintegrate into society following World War I. The majority of Americans in that era had never been more than a few hundred miles from their homes, let alone across continents. In addition, many men suffered from extreme trauma from the events they witnessed and participated in. A lot of jobs had been taken up by women, in the absence of male workers, and post-war society faced the problem of how to resolve this disparity.

The Eighteenth Amendment was the culmination of a decades long temperance movement that sought to end all alcohol sales, distribution, and consumption in America.  Initially celebrated as a progressive victory, the legal enforcement of prohibition proved a nightmare, and legions of criminal gangs began to control the illegal alcohol sales.  The Eighteenth Amendment was repealed by the Twenty First Amendment in 1933.

In Brown, Chief Justice Earl Warren expressed that in the arena of public education, "separate but equal" is inherently unequal, unfair, and unconstitutional. Plessy v. Ferguson is a prior case that upheld the "separate but equal" doctrine.

Black soldiers were almost exclusively placed in segregated units, away from their white compatriots. These regiments were usually commanded by white officers. Many black soldiers were held away from the primary areas of battle, this was generally a result of the racist view of many Americans that blacks were unfit or unwilling to fight with the same efficacy as their white peers. 

The decision in Brown v. Board of Education stemmed from a case brought by an African American family from Topeka, Kansas, challenging that city’s policy of having two school systems, one for white children and one for African-Americans.  The unanimous decision in Brown outlawed racial segregation in public schools throughout the nation as a violation of the Equal Protection Clause of the Fourteenth Amendment.

 On July 26, 1948, President Harry S. Truman signed Executive Order 9981, fully integrating every branch and level of the United States Military.  Secondary Schools and State College were not integrated by court order until the 1950s, while public transportation did not get fully integrated nationwide until the 1965 Civil Rights Act.  Prisons in the south were generally segregated until the 1970s.