Today, it may seem impossible to imagine the U.S. government without its two leading political parties, Democrats and Republicans. But in 1787, when delegates to the Constitutional Convention gathered in Philadelphia to hash out the foundations of their new government, they entirely omitted political parties from the new nation’s founding document.

This was no accident. The framers of the new Constitution desperately wanted to avoid the divisions that had ripped England apart in the bloody civil wars of the 17th century. Many of them saw parties—or “factions,” as they called them—as corrupt relics of the monarchical British system that they wanted to discard in favor of a truly democratic government.

“It was not that they didn’t think of parties,” says Willard Sterne Randall, professor emeritus of history at Champlain College and biographer of six of the Founding Fathers. “Just the idea of a party brought back bitter memories to some of them.”

George Washington’s family had fled England precisely to avoid the civil wars there, while Alexander Hamilton once called political parties “the most fatal disease” of popular governments. James Madison, who worked with Hamilton to defend the new Constitution to the public in the Federalist Papers, wrote in Federalist 10 that one of the functions of a “well-constructed Union” should be “its tendency to break and control the violence of faction.”

But Thomas Jefferson, who was serving a diplomatic post in France during the Constitutional Convention, believed it was a mistake not to provide for different political parties in the new government. “Men by their constitutions are naturally divided into two parties,’’ he would write in 1824.

In fact, when Washington ran unopposed to win the first presidential election in the nation’s history, in 1789, he chose Jefferson for his Cabinet so it would be inclusive of differing political viewpoints. “I think he had been warned if he didn't have Jefferson in it, then Jefferson might oppose his government,” Randall says.

George Washington (seated right) in consultation with Thomas Jefferson (seated left) and Alexander Hamilton. MPI/Getty Images

With Jefferson as secretary of state and Hamilton as Treasury secretary, two competing visions for America developed into the nation’s first two political parties. Supporters of Hamilton’s vision of a strong central government—many of whom were Northern businessmen, bankers and merchants who leaned toward England when it came to foreign affairs—would become known as the Federalists. Jefferson, on the other hand, favored limited federal government and keeping power in state and local hands. His supporters tended to be small farmers, artisans and Southern planters who traded with the French, and were sympathetic to France.

Though he had sided with Hamilton in their defense of the Constitution, Madison strongly opposed Hamilton’s ambitious financial programs, which he saw as concentrating too much power in the hands of the federal government. In 1791, Madison and Jefferson joined forces in forming what would become the Democratic-Republican Party (forerunner of today’s Democratic Party) largely in response to Hamilton’s programs, including the federal government’s assumption of states’ debt and the establishment of a national banking system.

By the mid 1790s, Jefferson and Hamilton had both quit Washington’s Cabinet. Meanwhile, the Democratic-Republicans and Federalists spent much of the first president’s second term bitterly attacking each other in competing newspapers over their opinions of his administration’s policies.

When Washington stepped aside as president in 1796, he memorably warned in his farewell address of the divisive influence of factions on the workings of democracy: “The common and continual mischiefs of the spirit of party are sufficient to make it the interest and duty of a wise people to discourage and restrain it.”

“He had stayed on for a second term only to keep these two parties from warring with each other,” Randall says of Washington. “He was afraid of what he called ‘disunion.’ That if the parties flourished, and they kept fighting each other, that the Union would break up.”

By that time, however, the damage had been done. After the highly contentious election of 1796, when John Adams narrowly defeated Jefferson, the new president moved to squash opposition by making it a federal crime to criticize the president or his administration’s policies. Jefferson struck back in spades after toppling the unpopular Adams four years later, when Democratic-Republicans won control of both Congress and the presidency. “He fired half of all federal employees—the top half,” Randall explains. “He kept only the clerks and the customs agents, destroying the Federalist Party and making it impossible to rebuild.”

While the Federalists would never win another presidential election, and disappeared for good after the War of 1812, the two-party system revived itself with the rise of Andrew Jackson’s Democratic Party by the 1830s and firmly solidified in the 1850s, after the founding of the Republican Party. Though the parties’ identities and regional identifications would shift greatly over time, the two-party system we know today had fallen into place by 1860—even as the nation stood poised on the brink of the very civil war that Washington and the other Founding Fathers had desperately wanted to avoid.