IN 1801 THOMAS JEFFERSON left his boardinghouse and walked a few hundred feet to the Capitol and delivered the first inaugural address given in Washington. A few months later, after Jefferson had moved into the White House, he owed Congress another speech, but this time he was careful not to go to Capitol Hill and deliver it himself. Instead, he had a clerk read it to Congress.

"The circumstances we now find ourselves in," Jefferson explained, dictated an end to the tradition of the president's appearing before Congress to speak on the state of the union.

The obvious question arises: Why didn't Jefferson give the speech in person? In the postrevolutionary capital, whenever the president called on Congress the congressmen were expected to politely return the visit. In his biography of Jefferson, Dumas Malone writes:

"How could so many carriages be found for the journey of a mile over the creek and through the swamp to the President's House?"

It was a vintage Washington swamp hypothesis, and it was wrong.

Nevertheless, every year when the humidity hits, a folklore returns to our media and penetrates the cafe's of Georgetown: All this unpleasantness of climate is inevitable because "the city was built on a swamp."

As a current example, take Susan Trausch's new book, It Came From a Swamp: Your Federal Government at Work. The author, a writer for The Boston Globe's Washington bureau, explained that she read up on the original Washington swamp in the World Book Encyclopedia, in an Arthur Frommer guide to the city and in a handout arguing for D.C. statehood that said the would-be state "was carved out of swampland."

All wrong, but quite understandable. Swamp is an irresistible metaphor for Washington. Swamp conjures up images of Pogo's "We have met the enemy and they is us." Calling Washington a swamp is the ultimate insider's put-down.

Enough, already, let us end the illusions: There was no swamp when Washington was founded. There was no stagnant water, there were no breeding places for mosquitoes downtown, there was no stench, no muck. Our favorite steamy little metaphor is all wet.

" . . . the lands within and surrounding the District of Columbia are as high, as dry, and as healthy as any in the United States," wrote George Washington in 1791.

On no 18th-century map of Washington is any area named or shaded as a swamp.

In one letter, Pierre L'Enfant mentioned "swampy" ground at the foot of Capitol Hill. He notes, however, that he toured the area after torrential rains and flooding.

Of the many letters and descriptions of Washington written between 1791 and 1801 that I've read, only one mentions a swamp. That one was written by a depressed congressman in the dead of the damp winter of 1801.

Kenneth Bowling knows more about the founding of Washington than any other historian. He has sifted through the evidence and found it dry. Bowling is currently editing the papers of the first Congress, the worthies who decided to put the capital on the Potomac.

"I've already heard two people on the subway this year telling tourists that Washington was built on a swamp," Bowling said. "I wanted to stand up and shout, 'It was not built on a swamp. THERE WAS NO SWAMP.' "

What visitors in the 1790s marveled at was the forests of Washington. "Excepting the streets and avenues, and a small part of the ground adjoining the public buildings," Isaac Weld wrote in 1797, "the whole place is covered with trees."

Trees do grow in swamps, but swamp trees didn't inspire this description of the banks of the Potomac River and Tiber Creek, which flowed where Constitution Avenue is today:

" . . . tall umbrageous forest trees of every variety," Margaret Bayard Smith recalled in her memoirs, "among which the superb tulip poplar rose conspicuous; the magnolia, the azalea, the hawthorn, the wild rose and many other indigenous shrubs grew beneath the shade, while violets, anemones and a thousand other sweet wood flowers found a shelter among the roots."

To people in 1800, swamps meant killer fevers. Twice secretary of the treasury Alexander Wolcott had to flee the temporary capital at Philadelphia because of yellow fever epidemics. After he got to Washington in July 1800 he wrote to his wife, "I perceive no reason for suspecting the city to be unhealthy," i.e., no swamp. Wolcott found his new situation "pleasant and indeed beautiful, the prospects are equal to those which are called good on the Connecticut River."

Another indication that there wasn't a swamp is that the man who owned the land where the swamp supposedly was refused to sell until he got a higher price. He was the only one of 13 landowners to hold out. It's hard imagining a man holding title to swampland playing hard sell. And George Washington did give him a higher price.

The city in 1800 differed physically from Washington today. The Potomac was wider; the lowlands that make up Potomac Park and Hains Point emerged from the river later in the century. There were bluffs along the Potomac. Tiber Creek, with a mouth about a quarter-mile wide just southeast of the White House, narrowed at Second Street and Pennsylvania Avenue, where it ran under a small bridge and then up to the hills beyond.

Kenneth Bowling has found no evidence that there was a swamp south of the Tiber where legend usually places it: "South of the Tiber was wet meadow and pasture, a plantation, not a swamp. There were tobacco fields, grain fields and oak and black cherry woodlots."

Then how did the myth of the swamp come to life? Probably because by 1816 every non-ornamental tree in the city had been cut down, including many of the forests in the hills overlooking downtown. Nature had provided man with a well-forested, well-drained area with undulating hills at the confluence of two large rivers. In short order men cut the trees and mucked up the natural drainage. So flooding of the Tiber became more frequent until the ground just west of the Capitol became permanently soggy. In addition, the city fathers had the great notion of turning the Tiber into a barge canal. All they managed to do was turn a once beautiful river into an open ditch.

But what about Thomas Jefferson who, according to Dumas Malone, justified changing national tradition because of a swamp between the Capitol and the White House?

"Swamp" is Malone's word, not Jefferson's. In a letter to Dr. Benjamin Rush, Jefferson gave the real reason for sending his message instead of giving a speech. Congressmen were paid by the day so Jefferson calculated that every day they met it cost the taxpayers $1,000. Jefferson wanted to cut taxes and pay off the national debt. His secretary of the treasury told him a shorter session of Congress would help. If Jefferson didn't go to the Hill, the congress wouldn't busy itself making up a response.

"I have prevented the bloody conflict to which the making of an answer would have committed them," Jefferson crowed to Rush. "They consequently were able to set into real business at once, without losing 10 or 12 days in combating an answer."

A president looking for economies and at the same time denying political opponents a chance to criticize him does not a swamp make.