Why the Supreme Court ended up with nine justices—and how that could change

Nine justices make up the U.S. Supreme Court: one chief justice and eight associate justices. But it hasn’t always been this way. For the first 80 years of its existence, the Supreme Court fluctuated in size from as few as five to as many as 10 before settling at the current number in 1869. Here’s how the court ended up with nine justices—and how that could change.

Constitutional foundations

When the Founding Fathers set out to establish the U.S. Supreme Court at the Constitutional Convention in 1787, they kept the details vague. There are no constitutional requirements for age, experience, or citizenship of Supreme Court justices, nor did the Constitution establish how many justices would make up the court. Instead, it left many of the details up to Congress and the president. (Here's why filling a Supreme Court vacancy in an election year is so complicated.)

Two years later, the first Congress passed the Judiciary Act of 1789—signed into law by George Washington on September 24, 1789—which established a court of six justices responsible for ensuring the constitutionality of laws enacted by the executive and legislative branches.

The law placed the Supreme Court at the top of a three-tier federal court system. At the lowest level, each state would have a federal judge presiding over district courts hearing minor cases related to federal laws as well as maritime cases. Those districts were then organized into three geographical regions with circuit courts that would both serve as trial courts and hear appeals.

Rather than create judgeships for each circuit court, though, Congress stipulated that two Supreme Court justices and one local district court judge would sit on circuit court panels. Each of the six justices was assigned a geographical circuit and required to preside over their circuit courts twice a year, meaning they were on the road for much of the year.

Partisan squabbles

It didn’t take long for the make-up of the courts to become a partisan issue. In 1801, Federalist party members in Congress sought to expand federal jurisdiction over the states by reorganizing the court system. Congress passed the Judiciary Act of 1801, creating new judgeships to serve six judicial circuits and reducing the Supreme Court from six seats to five. In so doing, the law also eliminated the practice of “riding circuit,” the cross-country travel which the Supreme Court justices detested.

Federalist John Adams, the second president of the United States, signed the bill into law on February 13, 1801. But the signing came just after he had lost his reelection campaign to political rival Thomas Jefferson, and the move was seen as an attempt to limit his successor’s appointments to the court. Jefferson quickly repealed the bill when he took office before any changes to the court’s composition could take effect. Since Supreme Court seats are lifetime appointments, the law had not removed any justices from the court but simply stipulated that the next vacant seat would not be replaced.

With the repeal, the six Supreme Court justices resumed their circuit riding duties. This time, rather than assign the justices to circuits, Jeffersonian Republicans instructed the six Supreme Court justices to allot themselves to the circuits “as they shall think fit.”

Westward expansion

During the next 70 years, the link between the Supreme Court justices and the circuit courts became the justification for the court’s fluctuating numbers. As the U.S. expanded westward—creating new judicial districts and circuits along the way—it needed more Supreme Court justices to preside over these circuit courts.

In 1807, the western districts of Ohio, Kentucky, and Tennessee lay outside of the established federal court system as they were difficult to reach across the Appalachian Mountains. District courts took on much of the circuit court’s duties instead. But as the volume of their cases increased, they pleaded with Congress to be reorganized into the existing federal judicial structure.

In response, Congress created the Seventh Circuit in 1807 and added a seat on the Supreme Court to match. The law also required that the new justice reside within the district to make the travel less arduous—a residency requirement that was never applied to another Supreme Court seat.

Thirty years later, in 1837, the admission of eight new western states to the union prompted Congress and President Andrew Jackson to add two more circuit courts—and two more justices, for a new total of nine, who would now be required to make even longer trips over difficult terrain to preside over the circuits.

Civil War

For the next couple of decades, the Supreme Court remained relatively stable. But then the Civil War arrived. In the early 1860s, Abraham Lincoln—who had sharply disagreed with the Supreme Court’s ruling in Dred Scott v. Sandford that Black people were not and could not become U.S. citizens—sought to reshape the court alongside his fellow Republicans in Congress. In 1863, an influx of settlers in California gave them an excuse to add a 10th circuit court and therefore a 10th Supreme Court justice.

After the Civil War ended, however, Congress once again changed the judicial system. In 1866, after Lincoln was assassinated and his vice president Andrew Johnson, a Southern Democrat, took over, Republicans in Congress worried about Johnson’s potential to influence the Supreme Court. At the time, Southern states were attempting to restrict the freedoms of newly-freed slaves with a rash of “Black codes” that prevented them from voting and limited the types of jobs they could hold. Johnson had also recently vetoed the Civil Rights Act of 1866, which would have placed a check on those states by granting citizenship and full protection under the law to all people born in the U.S.

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Though Congressional Republicans were able to override Johnson’s veto, they wanted to prevent him from tipping the Supreme Court in favor of the Southern states. They passed the Judicial Circuits Act, reducing the Supreme Court back to seven justices again.

But in 1869, the Republicans were back in control when Ulysses S. Grant assumed the presidency. They passed a new judiciary act that set the number of justices back to nine and required six justices present to form a quorum on decisions. Subsequent laws reduced the burden of circuit riding on the justices and, in 1911, ended the practice completely, severing the direct tie between the circuit courts and the number of Supreme Court justices.

Court packing

Since then, the Supreme Court has remained stable with nine justices serving on the bench. But that doesn’t mean politicians haven’t tried to change things up. Most famously, in the late 1930s, Franklin D. Roosevelt grew frustrated as the Supreme Court began striking down the New Deal laws he’d crafted to end the Great Depression. In February 1937, he floated the idea of increasing the membership of the Supreme Court to 15 justices.

The idea was wildly unpopular—even among Roosevelt’s supporters. It was described as “court packing,” an attempt to sway the court in his favor by creating new seats filled by justices he would be able to appoint and would thus likely be sympathetic to his policies. The Senate Judiciary Committee decried the president’s reform bill as “an invasion of judicial power such as has never before been attempted in this country.” Ultimately, the Senate voted against the plan 70-20.

Modern Supreme Court fights

The longstanding political tradition of reshaping the court has not died. In recent years, as President Donald Trump and a Republican-led Senate have overseen a shift in the U.S. Supreme Court’s political balance from moderate to conservative, liberals have begun arguing for a new expansion of the court.

This shift started in 2016 with the death of conservative justice Antonin Scalia. At the time, the court was split ideologically and, hoping to keep their conservative seat and prevent a liberal tilt to the court, Congressional Republicans refused to vote on President Barack Obama’s nomination of Merrick Garland to the court on the grounds that it was a presidential election year. Scalia’s seat remained vacant for nearly a year until Trump won the election and nominated Neil Gorsuch, who was seated in 2017. Though this appointment technically maintained the court’s ideological status quo, it laid the groundwork for the shift that came in 2018 with the retirement of Anthony Kennedy, a moderate who often had a swing vote on the court. Trump replaced Kennedy with associate justice Brett Kavanagh, a reliable conservative, shifting the court’s ideology further to the right.

Liberals fear that a conservative court will reverse several landmark decisions, including Roe v. Wade, which protects women’s right to abortion, and Obergefell v. Hodges, which recognizes same-sex marriage. It could also dismantle the Affordable Care Act, President Barack Obama’s signature health care legislation, as well as protections for immigrants. In recent years, the Supreme Court often split 5-4, meaning that even a slight shift in the court’s ideology could fundamentally shift the way it approaches these cases.

In 2019, Democratic presidential candidate Pete Buttigieg, then mayor of South Bend, Indiana, advocated for expanding the Supreme Court back to 15 justices with an aim to depoliticize it. According to his plan, five justices would be affiliated with Democrats, five with Republicans, and five would be apolitical and chosen by their colleagues.

On September 18, the death of associate justice Ruth Bader Ginsburg, a liberal icon who served on the court for 27 years, added to Democrats’ fears, as losing her seat would make the court even more ideologically conservative. Some prominent Democrats—including Massachusetts Senator Ed Markey—have stated that they would seek to expand or reform the Supreme Court if Ginsburg is replaced with a Trump nominee.

Democrats have offered several proposals for reshaping the Supreme Court. Some support Buttigieg’s plan to expand the court to 15 ideologically balanced judges, while others argue for a more partisan plan that would add two new seats on the court during the next Democratic presidency to counter the appointments of Gorsuch and Kavanaugh. Still others suggest imposing term limits on justices, arguing that more frequent turnover will reduce the intensity of the battles over each Supreme Court vacancy.

But the fate of these proposals remains unclear. Not only do they rely on Democrats winning majorities in Congress and retaking the White House in the elections this November, but as Roosevelt learned in the 1930s, sweeping changes to the court system require public support. In 2019, a Marquette University Law School national survey found that 57 percent of Americans oppose increasing the number of justices on the court—although 72 percent are in favor of imposing term limits. It remains to be seen whether support will rise for these measures in the wake of Ginsburg’s death.