Landmark cases involving the 14th Amendment
The 14th Amendment is the single most important amendment to the
Constitution requiring equal treatment under the law and extending civil liberties
to the state level. Below are some of the ground-breaking Supreme Court cases
it has been used in.

The Slaughter-House Cases (April 14, 1873) ―In the Slaughter-House
Cases, involved a Louisiana law over how slaughterhouse wastes were to be
handled. Meat packers challenged the law citing the 14th Amendment’s
Privileges and Immunities Clause as their remedy. The Court narrowly
interpreted the 14th Amendment saying the clause provided only a few obscure
privileges and immunities.. The ruling kept the door open for segregation laws
for the next 75 years..

Plessy v. Ferguson (May 18, 1896) ―The Louisiana legislature had passed a
law requiring black and white residents to ride separate, but supposedly equal,
train cars. In 1892, Homer Adolph Plessy challenged the law and appealed it to
the Supreme Court. In a 7-1 decision, the Court held that as long as the
facilities were equal, their separation satisfied the 14th Amendment. Justice
Harlan authored the lone dissent. Passionately he declared that the Constitution
was color-blind, railing at the majority for an opinion which he believed would
match Dred Scott in infamy.

Gitlow v. New York (June 8, 1925) ―Prior to 1925, provisions in the Bill of
Rights were not always guaranteed on the local level and usually applied only to
the federal government. Gitlow illustrated one of the Court’s earliest attempts at
incorporation, that is, the process by which provisions in the Bill of Rights have
been applied to the states. A socialist named Benjamin Gitlow printed an article
advocating the forceful overthrow of government and was arrested pursuant to
New York state law. Gitlow took the case to the Supreme Court which agreed
that the First Amendment applied to New York through the Due Process Clause
of the 14th Amendment. However, the Court ultimately ruled that Gitlow’s
speech was not protected under the First Amendment by applying the “clear
and present danger” test. The Court’s ruling was the first of many instances of
incorporating the Bill of Rights.

Brown v. Board of Education (May 17, 1954) ―It is impossible to mention
victories of the Civil Rights Movement without pointing to Brown v. Board of
Education. Following the Court’s ruling in 1896 of Plessy v. Ferguson,
segregation of public schools based solely on race was allowed by states if the
facilities were “equal.” Brown overturned that decision. Regardless of the
“equality” of facilities, the Court ruled that separate is inherently unequal. Thus
public school segregation based on race was found in violation of the 14th
Amendment’s Equal Protection Clause.
Engel v. Vitale (June 25, 1962) --  The Supreme Court ruled it
unconstitutional for state officials to compose an official school prayer and
encourage its recitation in public schools. The plaintiffs argued that opening the
school day with such a prayer violates the Establishment Clause of the First
Amendment as applied through the Fourteenth Amendment. This was another
example of how the 14th Amendment extended civil rights to the state level.

Griswold v. Connecticut (June 7,1965) ― The case was about whether the
Constitution protected the right of married couples to privately engage in
counseling and purchase of birth control. The decision said the Bill of Rights
contained a fundamental “right to privacy” that was protected by the 14th
Amendment’s Due Process Clause. Griswold’s “right to privacy” has been
applied to many other controversial decisions such as Roe v. Wade. It remains
at the core of substantive due process debate today.

Loving v. Virginia (June 12, 1967) ―Mildred and Richard Loving were an
interracial married couple who were charged with violating Virginia’s law
against such unions. The Supreme Court in a unanimous decision reversed the
Virginia Court’s ruling and held that the Equal Protection Clause required strict
scrutiny to apply to all race based classifications. Furthermore, the Court
concluded that the law was rooted in invidious racial discrimination, making it
impossible to satisfy a compelling government interest. The Loving decision
still stands as a milestone in the Civil Rights Movement.

Roe v. Wade (Jan. 22, 1973) -- This case relied heavily on the Griswold
decision that there is a right to privacy under the Due Process Clause of the
14th Amendment and it extends to a  woman's decision to have an abortion.
But that this right must be balanced against the state's interests in regulating
abortions: protecting women's health and protecting the potentiality of human
life.  Arguing that these state interests became stronger over the course of a
pregnancy, the Court resolved this balancing test by tying state regulation of
abortion to the last three months of pregnancy. In Planned Parenthood v Casey
(1992), the Supreme Court rejected Roe's trimester framework while affirming
its central holding that a woman has a right to abortion until fetal viability.

Obergefell v. Hodges (June 26, 2015) -- The Supreme Court decided that
same sex couples have the right to marry under both the Due Process Clause
and the Equal Protection Clause of the 14th Amendment. The ruling meant that
all 50 states must lawfully perform and recognize the marriages of same-sex
couples on the same terms and conditions as the marriages of opposite-sex
couples, with all the accompanying rights and responsibilities. Prior to
Obergefell, thirty-six states, the District of Columbia and Guam already issued
marriage licenses to same-sex couples.

Sources: National Constitution Center, Wikipedia