The Fourteenth Amendment to the Constitution—the linchpin of the current constitutional system—was ratified 150 years ago Monday, on July 9, 1868. July 9 marked the date on which the legislatures of South Carolina and Louisiana approved the amendment, bringing the total number of state approvals to the required 28 and inscribing the amendment in the Constitution for good.

Or, wait, hold that thought. In fact, before the approvals on July 9, the legislatures of Ohio and New Jersey had “withdrawn” their approvals—an action not provided for in the Constitution. The notifications of approval (like those of “withdrawal” before them) flowed, as a matter of course, to the office of Secretary of State William Seward, whose duty it was to keep track of proposed and adopted amendments.

On December 5, 1865, Seward had proclaimed that Alabama’s legislature had approved the Thirteenth Amendment, and its prohibition on “slavery or involuntary servitude” was now part of the Constitution; but three years later, in July 1868, Seward seemed to be temporizing. Though Seward had been appointed by Abraham Lincoln, he now served President Andrew Johnson—a virulent racist who had, during the elections of 1866, become the proposed Fourteenth Amendment’s most determined foe. At the time the amendment had been proposed in 1866, some had whispered that the secretary, at the direction of Johnson, might simply refuse to send the amendment to the states at all. Prudently, Seward had actually sent it forward without, apparently, consulting Johnson.

Johnson, however, had encouraged Southern legislators to reject the amendment, and they did. Ratification in 1868 came only after the Republican Congress took control of Reconstruction, and proclaimed that no state “formerly in rebellion” would be allowed to escape direct military rule until it approved the amendment.

Now, in 1868, Seward delayed for nearly two weeks before noting the approvals of July 9—and he noted them in a strangely conditional sense. “[I]t is deemed a matter of doubt and uncertainty whether [the ‘withdrawals’] are not irregular, invalid, and therefore ineffective,” he wrote in an official proclamation. If the withdrawals were ineffective, “the aforesaid amendment has been ratified … and has become valid, to all intents and purposes, as a part of the Constitution.”

Congress on the same day as Seward’s strange proclamation, passed a resolution declaring the amendment valid as part of the Constitution. Seward, a week later, finally officially certified its ratification.

In other words, American law is not even conclusive on when the Fourteenth Amendment become part of the Constitution. It was either Monday, or later this month—or maybe never; as late as 1957, pro-Southern commentators took the position that the amendment itself, having been imposed upon the South by Yankee scum, was not valid at all.

No one seriously claims that the amendment is invalid today; but every word, every part, and every effect of this most crucial of constitutional amendments has been fought over as bitterly as was the Bloody Angle at the Battle of Spotsylvania Court House.

That battle goes on today. It is, and has been for 150 years, a battle for the very heart of the American republic.

But, remarkably, the history of the amendment’s framing and ratification has been all but forgotten. Though at 425 words it is the longest and most important of all twenty-seven amendments, most law students study only its first section, and even that only as a jumbled set of half-understood phrases—“privileges and immunities,” “due process,” “equal protection,” etc. Since the very beginning of the amendment’s history, lawyers and courts have stepped forward to propose meanings for these terms that bear no relation to these terms. During the Gilded Age (and, increasingly, during this time), courts used the amendment as a means of enshrining the rights of capital over labor—outlawing pro-labor statutes and disarming legislatures that sought to regulate health and safety. During the age of segregation, and increasingly today, some courts read an amendment meant to protect racial minorities as an opportunity for legislation designed to subordinate them. Those meanings are only plausible to those who do not know the story of the amendment’s framing, or the names and lives of its framers.

Forgetting its own history, in other words, puts a nation at risk. A good exercise in patriotism this summer might be to study the true history of the Fourteenth Amendment. That story bears weird resemblances to the nation’s situation today, as once-solid certainties of the American constitutional order teeter on the verge of collapse.

To the members of the 39th Congress who framed the Fourteenth Amendment, the cause of the Civil War was clear. It was something called “the Slave Power”—a term which referred to the concessions made by the Philadelphia Framers to the slave states in 1787. Those were (1) the “three-fifths” clause, allowing extra seats in Congress to states with large slave populations; (2) the “electoral college,” which gave slave states undeserved power over the selection of the president; and (3) the principle of equal representation in the Senate, which had come over time to allow the South a veto over the more populous and dynamic North. As a result of this rigged system, the South had since 1790 dominated the White House, Congress, and the Supreme Court. And in the years after the 1857 Dred Scott decision, “the slavocracy” had begun making a legal argument that even “free states” must now be required to permit and protect slavery within their borders. The pro-Southern Supreme Court seemed quite likely to back such a radical new rule. “We shall lie down pleasantly dreaming that the people of Missouri are on the verge of making their state free,” Abraham Lincoln warned in 1858, “and we shall awake to the reality, instead, that the Supreme Court has made Illinois a slave state.”

Lincoln rode to victory in the presidential election of 1860 on a popular backlash against this Southern overreaching; unwilling to lose even one election, the South “seceded.”

The Union prevailed in the bloodiest war in American history. But Northern victory consumed much of the North’s strength—including Lincoln himself, its greatest weapon—and in its wake the “Slave Power” re-emerged, as determined as ever. Under the leadership of Lincoln’s successor, the Southern Democrat Johnson, the Southern states prepared to resume their domination over the nation. Abolition of slavery meant abolition of the “three-fifths” rule. That would boost the South, because it would get House seats and electoral votes for five-fifths of its black population—a population which, by order of the new president himself, would not be allowed to vote. By 1868, observers predicted, the South would dominate Congress and the White House, and gain compensation for slaves from its old handmaiden, the Supreme Court. (Fantastical rumors spread that the Democratic presidential candidate that year would be former Confederate General Robert E. Lee.)

Republicans in Congress worked frantically to remodel the Constitution before that could happen. They worked in the dark, against the determined opposition of President Johnson. The situation changed day by day; rumors swept the capital that Johnson would use his command of the Army to dissolve the existing Congress and install one of his own choosing. Although they originally planned a series of amendments to the Constitution dealing with specific areas, Republican leaders decided they had one chance—to write an “omnibus amendment” that would disable the “Slave Power” once for all.

Read in light of this story, the Fourteenth Amendment’s sections make sense. Section 1 sets out a standard of one uniform national citizenship, and of fair and lawful treatment for all persons in the U.S., regardless of race, and regardless of whether the person is an immigrant or a citizen. Section 2 tried to take the “five-fifths” windfall away from former slave states, by depriving them of House and electoral-college power for citizens to whom they denied the ability to vote. Section 3 disabled the leadership of the Confederacy from holding power in the postwar Republic. Section 4 guaranteed that the North’s war debts would be repaid, but that the South could not claim “compensation” for the liberation of its slaves. Section 5 put Congress, not the president or the (hitherto) pro-slavery Supreme Court, in charge of enforcing the new democratic rules.

The amendment’s unified aim was, as one of its supporters proclaimed, “a Union based upon universal liberty, impartial justice, and equal rights … a Union of truly democratic states.”

In the years after the Civil War, though, the idealism of the abolition crusade all but disappeared. Bit by bit, the “Slave Power” reassembled itself, with Southern elites using vote suppression, legal discrimination, and extralegal terror to maintain control over closed political systems, and using their members of Congress and their electoral votes to maintain disproportionate power in Washington.

The system was rigged again. The battle over that rigging is the heart of most post-Civil War American history.

To a surprising extent, in fact, the system today remains rigged along “Slave Power” lines. Dominance in the House and Senate falls to red-state governments that suppress voting and gerrymander districts, and undeserved electoral victory flows to popular-vote losers like George W. Bush and Donald Trump.

A century and a half later, Americans don’t agree on when the amendment was approved, and, I am sure, some in their hearts believe it should not bind the United States today. The battle of 1868 must be fought again, and so far it is not going well.

Facing that bleak reality may be the single most important patriotic observance Americans can engage in on the 150th anniversary of the Fourteenth Amendment. As Lincoln told the nation in 1862, “Fellow-citizens, we cannot escape history.” Neither God nor the Constitution can guarantee freedom if leaders cannot be called to account. On July 9, and July 21, and July 28, and every day forward, it is up to ordinary people—the same people who left shops and farms across the North to win the Civil War—to protect their own rights and those of others.