WASHINGTON (AP) — To Conrad Harrell of port-a-potty toilet supplier Don's Johns, Tuesday's inauguration of Barack Obama will be historic, but not in the way you might think.

"This is the largest temporary restroom event in the history of the United States," he said.

Don's Johns is providing many of the 5,000 port-a-potties for the inauguration, but other suppliers are at work as well, such as Mr. John, Johnny Blue and Johnny on the Spot.

In all, there will be 5,000 port-a-potties from about 10 vendors for Barack Obama's inauguration as president. On Thursday, they stood ready on the National Mall, port-a-potty-to-port-a-potty, some green, some blue, others gray.

The big question: will they be able to handle the call — er, nature's call — of the up to 2 million people?

"We think we've reached an appropriate number and can accommodate the crowds," said Kevin Griffis, a spokesman for the Presidential Inaugural Committee, a privately funded organization that is picking up the cost.

But Bill Line, a spokesman for the National Park Service, said there really was no way to say for certain.

"Ultimately, does anybody know how many people will show up?" he asked.

Line said that the Park Service recommends that organizers provide one port-a-potty for every 300 people, but stressed that it was up to the Presidential Inaugural Committee to decide whether to follow. At that ratio, 5,000 port-a-potties would handle 1.5 million people.

For other large events in the national capital, such as the July 4 Independence Day fireworks and the Cherry Blossom Festival of century-old Japanese cherry trees, there are usually around 800 port-a-potties, Line said.

Harrell said that Don's Johns, based in nearby Virginia, will have trucks on hand to handle any overflow situation, but attendants would hopefully pre-empt that by locking port-a-potties that fill up.

Organizers also point out that museums will be open for people to use bathrooms and escape from the cold. Griffis said the Presidential Inaugural Committee has paid the Smithsonian Institution $700,000 to open two of its museums, the National Museum of American History and the Smithsonian Castle, early at 8 a.m.

Harrell was confident there will be enough port-a-potties. "Absolutely," he said. "Absolutely."