The Slaughterhouse Cases overruled the Dred Scott v. Sanford case of 1857 and defined citizenship in a state and citizenship as a United States citizen based on the 14th Amendment. These cases are of great importance because they were the first ones to challenge the definition of state v. U.S. citizenship. The state powers gained by the ruling in the case did not last long because gradually the 14th amendment was used as a basis for broader federal protection for the interest of any private citizen.
In 1869, the state of Louisiana granted permission for a 25 year long monopoly to a small group of slaughterhouses in New Orleans and claimed it was in order to protect the health of the public. Butchers and slaughterhouse operators were barred from running their businesses and sued on the grounds that they had been deprived of property without due process of law, which they thought violated the 14th amendment. Upwards of 100 cases were involved, but the case that represented the overall decision of the court was Butchers' Benevolent Association v. Crescent City Livestock Landing and Slaughter-House Co.
An important point that the plaintiffs tried to make was that the 14th Amendment (passed in 1868) didn't just cover the rights of free blacks, but also of any citizens and private businesses. In 1873, the United States Supreme Court (with Justice Samuel F. Miller presiding) ruled against the Butchers' Benevolent Association and did not invoke the 14th Amendment by a vote of 5/4. The court decided that the original intent of the framers of the 14th Amendment had to be taken into account. The court perceived that their purpose was to guarantee the freedom of slaves, not to dictate the domain of the Federal Government over the states in civil rights cases. Therefore, they decided it was a matter of state, rather than Federal law.
Sources:
http://www.tourolaw.edu/patch/Slaughterhouse/
http://thestatecitizen.freeyellow.com/documentc2.htm
http://thestatecitizen.freeyellow.com/documentc1.htm