On June 9, 2004, the casket bearing Ronald Reagan’s body was carried up the steps of the US Capitol as “The Battle Hymn of the Republic’’ played. In the rotunda, under the great dome, military pallbearers laid the casket on Abraham Lincoln’s catafalque, where it was ringed by John Trumbull’s epic paintings of the American Revolution that hang on the rotunda’s walls.

The symbolism was intense. Trumbull’s four rotunda paintings — “The Declaration of Independence,’’ “The Surrender of Burgoyne at Saratoga,’’ “The Surrender of Cornwallis at Yorktown,’’ and “General George Washington Resigning His Commission’’ — have stood for two centuries as silent witnesses to the most august ceremonies of state and as ancestral sentinels connecting citizens and legislators to America’s origins.

These paintings germinated in the aftermath of the Revolution, came to life over the course of 30 years, and were the result of conversations between the artist and John Adams, Thomas Jefferson, James Madison, and James Monroe. Both the artist and the politicians understood that forging a new nation also required creating a shared identity — even national mythology — both at the time and for future generations. Today, political actors might acquire legitimacy through control of the media. In contrast, the fledgling American republic established itself in the public mind via monumental paintings.

Trumbull was one of five great American artists of the late 18th century — the others were Charles Willson Peale, John Singleton Copley, Benjamin West, and Gilbert Stuart — who invented the enduring look of the Revolution and its aftermath. The striking images they made — of the battles at Bunker Hill, Quebec, Saratoga, Yorktown, Princeton, and Trenton; the peace brokered in Paris; and the timeless portraits of Washington, Adams, Jefferson, Hamilton, Franklin, and others — illuminated the era. Even today, our collective understanding of what America’s early moments looked like is still largely dependent on these five artists and their renderings of reality.

Stuart’s portrait of Washington, as an example of durability and reach, has been reproduced more times than any other image in history. Besides the hundred or so versions that he painted himself and the thousands more — copies, prints, and copies of prints — that subsequently saturated American culture, Stuart’s portrait has adorned tens of trillions of $1 dollar bills since 1869. A full-length, life-size version of his Washington entered the White House in 1800, and each president from John Adams onward has had to measure his own tenure in office against its withering gaze.

All five artists started their careers as loyal British subjects. But the start of the Revolution in 1775 begged them to examine whether they intended to carry forward their inherited status or become contributing citizens in a new republic. As in no previous generation, they faced breathtaking historical changes that demanded to be painted for the people of their time and for posterity. Like everyone else, these artists had to confront the inherent incomprehensibility of the events swirling around them. They attempted to make sense of it all by turning to brushes and canvases. Works of art became their means of narrating the Revolution to themselves and to citizens of the new nation.

Because the United States quickly arose from a popular uprising, it was at first unstable and inchoate, and thus in urgent need of new images, rituals, and mythologies that not only could replace the old British ones, but that might also bring a disparate population together as a functional union. For most Americans, the notion of national citizenship was inherently incompatible with the cherished local identities by which they had been defining themselves for generations; each new state was, to some degree, a nation unto itself. While Americans might have comprehended the significance of independence from Britain, they did not necessarily grasp the full magnitude and enduring consequences of their newly acquired nationhood. John Adams explained the situation with acuity:

“The colonies had grown up under constitutions of government so different, there was so great a variety of religions, they were composed of so many different nations, their customs, manners, and habits had so little resemblance, and their intercourse had been so rare, and their knowledge of each other so imperfect, that to unite them in the same principles in theory and the same system of actions, was certainly a difficult enterprise.’’

Getting “thirteen clocks to strike together,’’ he added, would be an achievement that “no artist had ever before effected.’’

To be sure, helping Americans unite across region and culture were the shared rights and laws ultimately articulated in the Constitution, as well as political tracts and philosophical essays that made the case for the republic. But in order to fully bind together as a union, and not just a weak confederation of independent states, Americans required more than words. In such a perplexing and grave situation, persuasive images — of historic events, transcendent heroes, and honored martyrs — could be essential building blocks in the creation of nationhood because they provided a common vision of America.

The lives of these five artists were as colorful and exceptional as their paintings. Charles Willson Peale, who started life as a Maryland saddle-maker, wielded both a musket and a brush during the war. After the Revolution, he painted more than a hundred portraits of the worthies of his time, eventually installing them in a 100-foot-long gallery inside Independence Hall.

Benjamin West, born into a Pennsylvania Quaker family, moved to London in 1760, where he became the official historical painter to King George III. An American patriot at heart, West had to navigate his way through wartime England carefully, waiting for the day that he could express his American sentiments in words and pictures.

John Singleton Copley, the greatest painter in the Colonies, so craved political neutrality that he left Boston for London in 1774, where he made a spectacular debut into the British art world. At the end of the Revolution, he dropped his self-imposed rule of avoiding politics when he painted portraits of three American patriots, including John Adams on an impressive scale.

John Trumbull, son of the Colonial governor of Connecticut, served as General Washington’s aide-de-camp early in the war. Afterward, he painted some of the most stirring events from the war, and then, while living with Thomas Jefferson in Paris, he began work on his magnum opus, a painting of the Declaration of Independence.

Gilbert Stuart, born into a penniless Rhode Island family, was the most talented of them all. He was also a profligate perpetually courting disaster. Stuart painted just about every person who held power, or who wanted to. A man who never expressed a political allegiance, he was nonetheless responsible for the most memorable and enduring portraits of Washington.

These artists shaped the history of the United States — or at least how it’s remembered. They breathed visual life into historical events and figures, and over the centuries their images have become our indispensable icons, the American equivalents of what “The Iliad’’ and “The Aeneid’’ meant to the ancient Greeks and Romans. It’s a testament to their power that we see these paintings less as political documents than as a natural part of our national landscape.

As the United States accelerates toward a turbulent presidential election — its 58th, on the 240th year of the Declaration of Independence — these steadfast images can be called upon to remind Americans of where the nation came from and what it values most in its citizens and leaders. Without them, we would not be able to feel as grounded as we are in our past or as prepared to sustain our momentum into the future.

Paul Staiti is the author of “Of Arms and Artists: The American Revolution through Painters’ Eyes.’’