There’s a story that D.C. residents like to tell young interns whenever the summer weather gets particularly hot or sticky or unbearable.

The city, they say, was built atop a swamp, its location selected by George Washington. Washington wanted to be close to his  beloved Mount Vernon home (about 15 miles away). He cared little about D.C.’s heat index, the intense humidity, the never-ending heat waves.

It’s a great story, like the one about our first president chopping down a cherry tree.

But it isn’t true. At least, it’s not true enough to warrant its prevalence.

As an urban historian, I’ve studied the early geography of Washington for 40 years, and all the swamps I have found are itty bitty little things that would never have given a less politically vulnerable city a bad name. Russia’s St. Petersburg was built in the Neva River. New Orleans and Chicago were built in swamps, but that’s not what people most remember about them.

Within the original city’s boundaries (the area south of Florida Avenue), only about 2 percent of the total area fits the definition of a swamp. It was almost entirely laid out over well-drained terraces and hills. In fact, for a riverside site, it was amazingly free of swampiness.

It’s ironic that complaints about George Washington’s lacking common sense are often voiced by people standing on firm ground over a hundred feet above the city’s flanking rivers. My map shows that there were about 100 swampy acres in six separate areas in 1791.

1. In the city’s early days, the periodically-flooded area at the base of Capitol Hill was a problem that the shoddily built canal running through it did not solve. Instead of fixing the problem itself, the federal government handed the land over to private developers on condition that they drain it. Now the Capitol Reflecting Pool is where the swamp used to be.

2. The neighborhood of Swampoodle appropriately preserves the Irish pronunciation of “puddle” where the two main branches of Tiber Creek joined in a shallow valley. Drainage conditions got a lot worse before they got better for the immigrants who settled here in the mid-19th century.

3. Streams flowing out of the surrounding hills saturated the land where Le Droit Park was developed. A Florida Avenue combined sanitary and storm collector sewer only relieved local drainage problems for a while after it was completed in the 1880s.

4. The Anacostia River flowed too slowly to take away the effluent of the Florida Avenue sewer, so it settled on the foul tidal flats for decades while Congress refused to fund corrective re-engineering of the river.

5. The steep hills looming over the northwest perimeter of the city were drained by many small streams that saturated the sandy clay soil near S Street between 16th and 19th streets. Rising real estate values allowed this land to be improved before any substantial settlement occurred in the later 19th century.

6. Tiber Creek was first made into a canal, then into a sewer draining much of downtown. It flowed out onto the Potomac Flats, within easy smelling distance of the White House, and secured the city’s reputation for swampiness. Dredging the river solved that problem, with East and West Potomac Parks as pleasant and useful byproducts.

So the story that Washington was located in a swamp is a wild exaggeration based on selected facts: the common genes of political metaphor (Look no further than the 1986 dust jacket of “It Came From the Swamp” that showed the Washington Monument against a steamy orange background view of the Capitol and the city). For two centuries, our mythical swamp has been a handy introduction to arguments for lowering our expectations of government, the very business that the Constitution expected a Federal City to facilitate.