NEW YORK—On the eve of the international political conference in Pittsburgh known as the Group of 20, President Barack Obama addressed a packed main hall of the United Nations General Assembly in New York. Making his first appearance before the international diplomatic and peacekeeping body, Obama stressed that expectations of global cooperation now drive American foreign policy.

"In an era when our destiny is shared, power is no longer a zero sum game," he said. "No world order that elevates one nation or group of people over another will succeed. No balance of power among nations will hold. The traditional division between nations of the south and north makes no sense in an interconnected world."

After eight years of unilateralism under George W. Bush, the message of outreach and inclusion was received with enthusiastic applause. But as Obama lands in Pittsburgh, it's worth remembering that until recently, a smaller, more elite group of eight countries dominated global discussion. Leaders from those nations will have their own meetings during the two-day conference devoted to climate change, nuclear security and restabilizing the global economy. Yet it’s almost guaranteed that you'll hear more about the G20 than the G8. Suddenly, the organization, created in 1975, is "no longer the board of directors of the world," but a more inclusive organization, said David Wessel of the Wall Street Journal, while addressing the Council on Foreign Relations last week.

But just when did the G8 become the G20?

Originally, the G8 was the Group of 7—which included finance ministers from the U.S., Great Britain, France, Germany, Italy, Canada and Japan. In 1998, it became the G8 for "political reasons," according to former President Bill Clinton. The massive and resurgent Russian Federation could no longer be credibly excluded from the debate. Similarly, says Clinton, the dozen other countries at this week's G20 gathering have earned a seat at the table by representing the increasingly diverse elements of a more interdependent world order. "It's not a bipolar world, as it was during the Cold War, not a polar world, as it was briefly in the aftermath of the Cold War," Clinton told The Root.

The first informal meeting of an expanded group of major powers was in 1998, when Clinton convened 22 nations in Washington in the aftermath of that year’s brief financial crisis. The short-lived G33, including many countries that are now part of the European Union, was conceived shortly thereafter—and the G20 had its first meeting in Berlin in late 1999. The new configuration, primarily focused on financial and economic coordination, added representation from Latin America, Africa and Southeast Asia—and finally included major developed economies like South Korea and Australia.

Today, Turkey is a portal to the Middle East and “a bulwark against Islamic extremism,” according to Clinton. Economic growth in Argentina, Mexico, China and South Africa has transformed world trade; and partnership with major emitters in Asia and oil producers like Saudi Arabia are critical to moving forward on a heated debate on global climate change. “Sooner or later China and India were going to be at every meeting anyway,” adds Clinton. "These 20 have a lot of the world’s GDP, and a lot of the world's best ideas."

"It's a maturing, a transition," says Sen. John Kerry, D-MA, chairman of the Senate Foreign Relations Committee. "I think people realized that these were countries of great importance and economic strength, and it's going to take a larger universe to solve some of these problems." Rev. Jesse Jackson welcomes the development as a statement about rights and equality. "I think it makes a world of sense," he said while attending the Clinton Global Initiative in New York. "You've brought Africa to the table; you have more poor people represented."

Some think it was the financial crisis that precipitated an expanded world order. The full Group of 20 has formally met only a handful of times, with accelerating participation after the September 2008 global financial market failures. “It's obviously easier to have a global consensus when people are scared, as they were in London," says Dominique Strauss-Kahn, the head of the international Monetary Fund (IMF), referring to the panicked G20 meetings of late 2008 and early 2009. Then, the larger body was able to make strong, coordinated moves toward rescuing the global economy, pledging together $2 trillion in stimulus funding and launching a $20 billion food security initiative geared at building capacity and stopping hunger among developing nations.