Robert Cooper Grier (March 5, 1794 – September 25, 1870) was an American jurist who served on the Supreme Court of the United States.

As one of two Northern members of the majority in the Dred Scott v. Sandford (1857) decision, Grier concurred that African Americans were not and were never meant to be citizens of the United States and that the property rights of slaveholders were clearly protected in the U.S. Constitution, after being pressured by President-elect James Buchanan to join the Southern majority in an attempt to prevent the appearance that the decision was made along sectional lines.

In 1833, Grier was rewarded with a patronage appointment to a judgeship on the Pennsylvania State District Court for Allegheny County, which seat was newly created for him.

[3] Associate justice of the United States Supreme Court Henry Baldwin died in April 1844, during the presidency of John Tyler.

Twice Tyler attempted to fill the vacancy, nominating first Edward King and then John M. Read – both were rejected by the United States Senate.

[1] There had been an 841 day-long gap between the death of Henry Baldwin (April 21, 1844) and Robert Grier's swearing-in, which is the longest vacancy in the history of the U.S. Supreme Court.

[5] Grier's most significant contributions to the Supreme Court and the Constitution are found in his decisions regarding slavery, particularly Dred Scott v. Sandford, and his support of the Union in the Prize Cases.

He believed that, because he had made this decision under Maryland's insolvency laws, he escaped from all debts, including those that he owed to citizens and companies in other states.

In his first majority opinion, Grier ruled in favor of Moffat and Curtis, finding that a State shall not "inflict her bankrupt laws on contracts and persons not within her limits.

Citing multiple opinions, Grier remarked that holding in favor of Cook would "overrule every case heretofore decided on this most difficult and intricate subject."

The charter granted the RFP sole rights to transport passengers between Richmond and Fredericksburg for a period of thirty years, thus establishing a contract between the company and the state.

"[11] Nonetheless, the committee's report is intriguing because it was authored by Hendrick B. Wright, who was a fellow Dickinson alumnus and defeated for reelection in the next Congress, indications of probable bias in the justice's favor.

Though Grier ultimately did not convict Castner Hanway of treason for his role as a bystander when a mob of African Americans killed a slave owner and a federal marshal attempting to recover fugitive slaves, Grier uttered harsh words against abolitionists, describing them as "infuriated fanatics and unprincipled demagogues" who "denounce the constitution, the laws, and the Bible.

Certainly, Grier's mind throbbed with these beliefs about abolitionists and African American freedom when Dred Scott came before the Supreme Court.

By suing Sandford, a citizen of New York, Scott enabled the Supreme Court to become involved, as this constituted a suit between people of different states.

Wanting to change his peer's mind, Justice John Catron wrote to President-elect James Buchanan and asked him to lobby Grier for a broader opinion.

"[15] Breaching separation of powers and siding with the majority, the Dred Scott case struck a blow to Justice Grier's historical reputation.

[17]During the American Civil War, Grier discontinued circuit riding in 1862, and in 1863 wrote the opinion on the Prize Cases, which declared that Lincoln's blockade of Southern ports was constitutional.