In the Pan American Union building competition of 1907, upstart architect Paul Philippe Cret beat out established firms by diverging from predictable classical construction.

Absorbing the mission of the union, eventually renamed the Organization of American States, Cret harmonized Western norms with Latin American style to design a one-of-a-kind structure that stands apart from its Washington, D.C., contemporaries.

April 26 marked the 100th anniversary of the building’s inauguration, the first in what would be Cret’s decades-long career of important unveilings, including the Marriner S. Eccles Federal Reserve Board Building, Philadelphia’s Benjamin Franklin Bridge and the campus of the University of Texas at Austin.

To celebrate the OAS building and the man behind it, the Art Museum of the Americas presents “House of the Americas Turns 100: Paul Philippe Cret and the Architecture of Dialogue.”

“It’s really important that he made a dialogue between Latin American figures and classical architecture,” said the museum’s education coordinator, Adriana Ospina. “He actually learned the agenda of the organization, and on that base, he constructed the building.”

A hemispheric headquarters for the Americas was the notion of President Theodore Roosevelt, but it was his successor, William Howard Taft, with funding from Andrew Carnegie, who saw the idea through. Then housing 21 nations and now 35, the organization represents regional solidarity, and it needed a building that would convey the same message.

But the 1907 contest was rife with submissions of cautious plans for the organization that would stand just a stone’s throw from the White House; imposing domes and colonnades dominate the entries, which are on display as part of the exhibit.

Cret, though, travelled to Mexico to research its architecture. His sketchbooks from the adventure are on display and show how the experience affected his final plan.

What Cret came back with was an ambitious project that, as the curatorial description puts it, “presents a series of dialogues — between function and aesthetic, artifice and nature, and perhaps most memorably, between the Classical architecture that defines much of the nation’s capital and the architectural traditions, both ancient and colonial, of Latin America.”

Two wide pilasters separated by three round arches depict in reliefs the emancipation of the Americas from colonial rule: On the right, under an eagle, Gen. George Washington dismisses his generals after the Revolutionary War; on the left side, a condor sits atop the fabled meeting between Simón Bolívar and José de San Martín to plan the future of Latin America.

Walking through the classical arches, visitors are instantly transported into Latin America. A foyer there resembles a colonial city square with an ornate fountain set upon Aztec tile motifs, such as a subordinate offering a pineapple to a king or God.

Plants indigenous to North, South and Central America and the Caribbean grow inward from the foyer’s four corners. The original “Peace Tree,” a hybrid of fig and rubber, planted by Taft at the inauguration, now stands as tall as the retractable roof overhead.

Up two marble staircases, the Hall of Flags and Heroes houses busts of important figures and every member nation’s flag.

Just beyond it lays the Hall of the Americas, where massive Corinthian columns support a spectacular barrel-vaulted room with Tiffany chandeliers and stained-glass windows that overlook a backyard reflecting pool. Xochipilli, the Aztec god of flowers, sits guard over the water.

What is most incredible about the exhibit, though, is that the museum (built by Cret to be the residence of the organization’s head) is directly behind the OAS building. After learning all about the background, visitors can simply walk into the building itself, which, like the museum, is free and open to the public.

The exhibit runs through July 3.