Washington, DC was not built on a swamp. The terrain that became the nation’s capital included tidal marshes along the Potomac and Anacostia rivers, but the city’s core sat on a series of hills and river terraces well above the waterline. The “swamp” label owes more to political rhetoric and the region’s humid summers than to any honest reading of the landscape, though the story is more interesting than a simple myth-busting exercise suggests.
What the Land Actually Looked Like
When George Washington selected the diamond-shaped federal district in 1790, the site was not a featureless bog. The land rose from the rivers in a series of terraces and rolling hills, some reaching more than 100 feet above sea level. Jenkins Hill, where the Capitol now stands, was one of the most prominent of these. Georgetown, already a functioning port town on the Potomac’s north bank, occupied bluffs overlooking the river. The Eastern Branch, now called the Anacostia River, met the Potomac at the district’s southern edge, and both waterways were bordered by tidal flats and freshwater marshes that flooded and receded with the tides.
These tidal marshes were real, and they were extensive in some areas. But a tidal marsh is not a swamp. Swamps are forested wetlands with standing water much of the year. Tidal marshes are grassy or reedy flats along estuaries, shaped by the daily movement of water. The distinction matters because calling the whole site a swamp implies that someone drained a vast, sodden wasteland to build a city, which is not what happened. The city’s major buildings and residential neighborhoods were placed on high, dry ground from the start. What the builders did eventually reshape was the low-lying ground between the river and the hills, and that story came later.
How the Myth Took Hold
The swamp narrative has been circulating for well over a century, and it stuck because it works on multiple levels. Early residents of Washington genuinely hated the climate. Summers were brutally hot and humid, mosquitoes bred along the river margins and in the sluggish creeks that wound through the area, and malaria was a recurring problem into the 19th century. Visitors from northern cities found the conditions miserable and described Washington in the most unflattering terms they could manage. “Swamp” was a natural shorthand for a place that felt tropical, buggy, and unfinished.
The metaphor also gained political traction. By the early 20th century, “draining the swamp” had become a figure of speech for cleaning up government corruption. The phrase was too useful to let go. It implied that Washington was not just politically rotten but geographically rotten, a city that should never have been built where it was. The literal and figurative meanings reinforced each other until most people assumed the literal version was true. Historians and geographers have pushed back on this for decades, but the myth has a momentum that corrections struggle to match.
There is also a simpler explanation: people conflate wetlands with swamps. The Potomac floodplain did include marshy areas, and Tiber Creek, a small waterway that once ran roughly along what is now Constitution Avenue, created muddy, low-lying terrain in the middle of the developing city. These features were inconvenient, smelly, and visually unappealing. Calling them a swamp was not a scientific classification. It was a complaint.
Tiber Creek and the City’s Lost Waterways
One of the most important features of the original landscape was Tiber Creek, which flowed from the hills north of the city southward to the Potomac, passing through what is now the heart of the National Mall. In the early decades of Washington’s existence, the creek was an open waterway that occasionally flooded and served as a dumping ground for waste. It became a serious public health nuisance as the city grew. By the mid-1800s, the Army Corps of Engineers began enclosing the creek in a sewer, and eventually it was buried entirely beneath the city’s streets.
Other small streams and springs dotted the district. Rock Creek, which still flows through its namesake park, was the largest. The Anacostia’s tributaries created marshy lowlands on the city’s eastern side. These watercourses shaped early development patterns. Buildings and neighborhoods clustered on the higher ground between drainages, and the lower areas remained undeveloped or were used for agriculture. The presence of these creeks and their associated wet margins is part of what people remember, or misremember, as the “swamp.” But every city built along a river has low-lying wet ground near the water. Washington was not unusual in this respect.
The Land That Was Made, Not Found
If the original site was not a swamp, parts of the Washington that tourists visit today do sit on land that was artificially created. The western end of the National Mall, the Tidal Basin, and the ground beneath the Lincoln Memorial and the Jefferson Memorial were all produced by dredging and filling in the late 19th and early 20th centuries. The Army Corps of Engineers pumped sediment from the Potomac riverbed to extend the shoreline and create usable land where tidal flats had once existed.
The engineering consequences of this are significant. All of the structures from the Washington Monument west to the Potomac River sit on fill composed of sand, gravel, and blue clay. A 1950 U.S. Geological Survey report found that the Washington Monument’s 25-foot-deep foundation rests roughly 65 feet above bedrock, with that fill material in between. This type of substrate is vulnerable to soil liquefaction during earthquakes, which means the ground can behave more like a liquid than a solid when shaken hard enough.1NOAA Institutional Repository. Project report, leveling of the Washington Monument and the Washington Mall
The 2011 Virginia earthquake, centered about 80 miles southwest of the city, provided a real-world test. The Washington Monument sustained visible cracking and was closed for repairs for nearly three years. The ground beneath the monument and its neighbors is simply not the same as the ground beneath the Capitol or the White House, which sit on natural terraces with much shorter distances to solid rock. So the irony is this: the parts of Washington that most resemble a drained wetland are the parts that were built on manufactured land, not the original city site.
The Soils Beneath the City
Soil scientists have a specific way of identifying land that spends significant time saturated with water. A soil classified as “hydric” has conditions that favor the growth of wetland vegetation, and it serves as a marker that the ground is or was part of a wetland system. The U.S. Department of Agriculture’s soil survey database includes hydric soil ratings for every mapped soil unit in the country, including the District of Columbia.2U.S. Geological Survey. Area- and depth- weighted averages of selected SSURGO variables for the conterminous United States and District of Columbia
In DC, hydric soils show up where you would expect: along the Anacostia and Potomac riverfronts, in low-lying areas near old stream channels, and in spots where fill was placed over former tidal flats. They do not blanket the district. The higher ground that makes up most of the city’s residential and governmental core has well-drained soils typical of the mid-Atlantic Piedmont region. This is consistent with what the historical record shows. The site was chosen in part because it offered a mix of river access and elevated building ground, and the soils confirm that the elevated areas were genuinely dry.
Flooding Past and Present
Even though the city was not a swamp, water has been a persistent challenge. Washington sits at the head of the Potomac estuary, where the river transitions from fresh to brackish, and the combination of river flooding, tidal surges, and storm events makes the area one of the most flood-prone stretches of the U.S. East Coast. A 2025 study analyzing 500 years of flood evidence found that DC faces one of the highest 100-year flood risks of any major city along the eastern seaboard.3Geophysical Research Letters. Extreme Potomac Floods at Washington D.C. During the Past 500 Years
The flood risk comes from multiple directions at once. Hurricanes and nor’easters push storm surges up the Potomac from the Chesapeake Bay. Heavy rainfall in the Potomac watershed sends river floods downstream. And the two can combine. Historical water-level records for Washington are heavily skewed by these major Potomac flood events, meaning the city’s flood statistics look worse than those of many coastal cities that face storm surge alone. Early surveys of the Capitol Building and other landmarks suggest that sea level on the Potomac at Washington has risen by roughly 0.7 meters, or about 2.2 feet, since the 1790s.3Geophysical Research Letters. Extreme Potomac Floods at Washington D.C. During the Past 500 Years
That rise is a combination of global sea-level increase and regional land subsidence. The mid-Atlantic coast has been slowly sinking since the last ice age, as the land that was pushed up by the weight of glaciers to the north continues to settle back down. This means that even without accelerating climate change, the Potomac’s waterline would be gradually creeping higher relative to Washington’s streets and foundations.
What Rising Seas Mean for the Capital
Future projections make the flood picture considerably worse. A risk analysis of sea-level rise impacts on Washington estimated that even a modest rise would cause at least $2 billion in direct property losses based on real estate assessments alone, without counting infrastructure damage to military installations, government buildings, or cultural institutions. Under a more extreme scenario of 5 meters of sea-level rise, projected property losses exceed $24.6 billion.4PubMed. Prediction and impact of sea level rise on properties and infrastructure of Washington, DC
The areas most vulnerable are exactly the ones you would predict from the city’s geological history. The filled land along the Potomac, the low-lying neighborhoods along the Anacostia, and the areas built over former tidal marshes and stream channels face the earliest and most severe inundation risk. The National Mall, the Tidal Basin, and the memorials on filled ground are all in this zone. Higher-elevation neighborhoods like Capitol Hill and the areas around Dupont Circle face much lower risk, because they sit on the natural terraces that made the site attractive in the first place.
The practical consequence is that the parts of Washington most people picture when they think of the city, the monumental core along the Mall, are also the parts most exposed to water damage in the coming decades. The ground beneath them was made by engineers, and the river is gradually reclaiming its margins. Whether that counts as “the swamp coming back” depends on how loosely you define your terms.
L’Enfant’s Design and the Role of Topography
Pierre Charles L’Enfant, the French-born architect who designed Washington’s street plan in 1791, was acutely aware of the terrain. His plan placed the Capitol on Jenkins Hill specifically because it was the most commanding high point, with clear sightlines in every direction. The President’s House went on a separate ridge to the northwest. L’Enfant connected the two with a broad diagonal avenue, now Pennsylvania Avenue, and laid out a grid of streets interrupted by grand radial avenues that followed the natural contours of the hills and valleys.
The design was not the work of someone trying to build on a swamp. It was the work of someone using topography to dramatic effect, placing buildings where they would be visible and impressive. The low ground between the Capitol and the river was intended as a canal and public garden, not as a building site. L’Enfant imagined the waterfront as an asset, with wharves and commercial activity along the rivers. The fact that these low areas later became the city’s most celebrated public spaces, through decades of filling and grading, was not part of the original vision.
Tidal Marshes Return to DC
In a twist that would surprise the “drain the swamp” crowd, Washington has been actively restoring tidal wetlands in recent decades. Along the Anacostia River, several restoration projects have rebuilt freshwater tidal marshes that were destroyed or degraded by centuries of development, pollution, and sediment runoff. Researchers studying the seed banks of these restored marshes have documented the return of native wetland plant communities, suggesting that the ecological potential of the Potomac estuary’s margins remains intact even after centuries of urban use.5Urban Ecosystems. The seed bank of a restored tidal freshwater marsh in Washington, DC
These restored marshes serve practical purposes beyond ecology. Tidal wetlands act as natural sponges during storm events, absorbing floodwater and slowing its spread into developed areas. They filter pollutants from stormwater runoff before it reaches the rivers. And they provide habitat for fish, birds, and other wildlife in one of the most heavily urbanized estuaries on the East Coast. The city that was falsely accused of being a swamp is now spending real money to bring wetlands back, not because it was wrong to build there, but because functional wetlands make the city more resilient to the water challenges it has always faced.
The restored sites are small compared to the marshes that once lined both rivers, but they represent a shift in how the city thinks about its relationship with water. For most of its history, Washington treated every creek, marsh, and tidal flat as a problem to be buried or filled. The current approach treats at least some of that water as infrastructure, a natural system that does useful work if allowed to function. That pragmatic turn may end up being more important than the question of whether the original site was technically a swamp, because the water is not going away. If anything, there will be more of it.