The Fourteenth Amendment to the Constitution of the United States is one of the post-Civil War amendments, and includes, among others, the Due Process Clause and the Equal Protection Clause. It was proposed on June 13, 1866, and ratified on July 9, 1868.
The amendment provides a broad definition of national citizenship, which overrides the decision of Dred Scott v. Sandford (1857), who had excluded slaves and their descendants, from possessing constitutional rights. It requires states to provide equal protection before the law to all persons (not just citizens) within their jurisdictions. The importance of the Fourteenth Amendment was exemplified in the 1950s when it was interpreted to prohibit racial segregation in public schools in the case Brown v. Board of Education.
The Declaration of Independence was the u.s. telling Great Britain that we wanted to be independent from them. The Constitution is the laws and principles of the Untied States. When something is questioned to be legal the constitution is consulted.