An abandoned canal with overgrown grass and brush.
The Patowmack Canal was created to make a 218 mi stretch of the Potomac River navigable. (Photograph courtesy of

By Leslie Nemo

George Washington’s first stint as a president was not with the U.S. government; it was with the Patowmack Co. Founded in the 1780s, the organization was established to improve navigation on a 218 mi stretch of the Potomac River. By the time of the project’s substantial completion in 1802, five bypass canals, collectively known then as the Patowmack Canal, had been built to “skirt” the river’s rapids (or falls).

The most complex and ambitious portion of the project was at the Great Falls location, where not only a bypass canal was built but a series of five locks as well. Remnants of this undertaking, now known as the Great Falls Canal and Locks, in northern Virginia, record one of the earliest attempts at canal technology in the United States.

The series of five locks compensated for an almost 80 ft (76 ft, 9 in.) elevation drop, a feat made more impressive by the fact that hardly anyone who worked for the Patowmack Co. had ever seen such a structure before. However, a lack of information and expertise about how to build the canal system, as well as overcoming the physical obstacles in the river itself, led to a host of problems for the company, eventually leading to its failure.

But for the Patowmack Canal, its construction and existence influenced the design and funding of subsequent American engineering projects.

Though using the Potomac River as a route into the Ohio River Valley had appealed to European-American settlers for decades, navigating the waterway was challenging. It had been one of Washington’s personal goals to make the trip easier since at least 1770, when he started claiming thousands of acres in the Ohio area.

In 1784, about a year after the conclusion of the Revolutionary War, Washington and some like-minded individuals campaigned to make the river modifications happen. Since no federal government existed in 1784 (it would not be formed until 1789), Washington and his colleagues wrote letters, put forth a petition, and made visits to politicians of Maryland and Virginia — states that bordered the Potomac River — for company charters.

Eventually, Washington and his compatriots were successful. The plan to improve navigation conditions on the Potomac River received official approval: a company charter from the Maryland legislature in 1784 and another from Virginia in 1785. The documents authorized the newly formed Patowmack Co. to improve navigation from as far north on the river as possible down to Georgetown in Maryland.

This agreement was “the first interstate internal improvement project that required the cooperation of more than one state government and contemplated linking two major regions of the country,” according to Douglas R. Littlefield in the article, “The Potomac Company: A Misadventure in Financing an Early American Internal Improvement Project” (The Business History Review, Winter 1984, Vol. 58, No. 40).

An abandoned canal set in the landscape.
Shovels, sledgehammers, picks, and drills were used to hand-carve the canal. Shown here is the abandoned lock 1 at Great Falls. (Photograph courtesy of Bernie Dennis)

According to the charters, adjustments to the river itself, such as removing obstacles, had to be completed in three years, while major construction to bypass the multiple falls had to be finished in a decade. The charters also permitted the company to raise as much as 50,000 pounds sterling to accomplish the work by selling shares. By the first stakeholder meeting on May 17, 1785, the company, helmed by Washington, had sold 400 so-called “subscriptions.”

With plans to start the river improvements in what is now the West Virginia town of Harper’s Ferry, the company’s directors identified five falls to be navigated around. All of them (House Falls, Shenandoah Falls, Seneca Falls, Great Falls, and Little Falls) required skirting canals or sluices. Though some of the founding members of the company were surveyors, they knew where their technical skills ran out: The company needed a trained engineer to design locks at Great and Little falls, the two largest sites. Washington suggested the team bring in an expert from Europe. Instead, the company landed on local mechanical engineer, inventor, and steamboat tinkerer James Rumsey.

Photo shows a wall made of overlapping stones built to divert water.
This rock wall diverted the river so that boats could avoid a small island in its center. (Photograph courtesy of DHR)

Construction kicked off on Aug. 5, 1785, when hired laborers began pulling obstructions from the riverbed. Work in the Potomac River expanded to include minor construction projects that subtly reshaped its boundaries.

Workers straightened banks and built small dams or in-river sluices to deepen water where necessary. One structure in the vicinity of Great Falls still exists today. Stretching about 263 ft and made of overlapping stones, it diverted the river so that boats could dodge a small island in its center.

In March 1786, Rumsey and his workers began cutting the canal for Great Falls. Shovels, sledgehammers, picks, and drills helped them hand-carve a 1,200 yd canal alongside the Potomac that was 25 ft wide at the surface, a dimension the charters dictated to meet the needs of typical boats of the time.

Laborers also built a wooden crib (or wing) dam that was filled with stones, which arced into the river and guided water into the canal. A small, local stream was rerouted into the canal as a backup water source, while a 25 ft wide masonry dam spillway allowed any overflow to escape.

Also in 1786, the first round of recurring troubles appeared. In July, Rumsey quit his role a few months after starting construction at Great Falls. At least four other engineering experts would be brought on as temporary advisers or hired — and then dismissed — over the course of the project. What’s more, around the time Rumsey left, Patowmack Co. funds started running low. The project implemented a pay-as-you-go system in which shareholders gave in increments as the directors requested funds. By the end of 1786, less than half the calls for stockholder contributions had been met.

In Washington’s second annual report, issued in 1787, he shared that the Great Falls canal was nearly complete. Construction on the Great Falls Locks should have started next, but instead, the company and its workers hesitated for several years, unsure of how to do the work without the guidance of an on-staff engineer.

Labor was also difficult to secure. The company began by relying on hired men. But as pay disputes increased, the directors turned to indentured servants and enslaved workers. The former, realizing they were working in remote locations, often ran away. Ultimately, most of the Great Falls system was built by enslaved individuals “rented” from nearby plantations.

Some of the only construction progress the company managed at the time was downstream at Little Falls. At this location in the river, the cascades required a roughly 2.5 mi canal and three locks, which the company crafted from wood. In August 1795, the completed construction at Little Falls received a seal of approval when test boats made it through the locks safely, just in time for work to pick back up on Great Falls.

Though physical work progressed, financial troubles loomed again. In the mid-1790s, the company directors sold additional shares to bring in more funding. On a positive note, they were able to convince British engineer William Weston to provide advice on the design of the locks at Great Falls. Working on another project in the region, Weston traveled through the site, suggesting a slightly new alignment for the locks.

In January 1796, the next engineer installed on the Great Falls project, a Brit named Christopher Myers, picked up as Weston suggested. Under Myers’ direction, the company sourced stone for walls and white oak for the guard and lock gates. But Myers was not to last. The directors fired him in May 1797 for being challenging to work with.

In his place came Leonard Harbaugh, an experienced builder from Baltimore, who had no formal training in “river improvement technology” but had overseen the construction of the Little Falls project, states Littlefield in the article, “Eighteenth-Century Plans to Clear the Potomac River: Technology, Expertise, and Labor in a Developing Nation” (The Virginia Magazine of History and Biography, 1985, Vol. 93, No. 3).

Though Harbaugh would lead the completion of the Great Falls Canal and Locks, the company had yet another financial crisis before he made much progress.

Struggling in a post-Revolutionary War economy with massive debt and spending more than it expected on the project, the company was out of money by the end of 1797. Fortunately, the two state governments intervened: The Maryland and Virginia legislatures gave the project the final funding it needed. The states allowed the company to charge tolls for goods transported along the route, provided the company found a way to haul items on land around existing construction sites, and Maryland bought 130 shares “of a third stock issue,” according to Littlefield in his Business History Review article.

Washington, who checked in on the project regularly after stepping down from the company to serve as president of the U.S., did not get to see the canals and locks completed. He died in December 1799, less than three years before completion of the Patowmack Co. project.

With cash flow renewed in 1800, Harbaugh and his workers completed the last and possibly hardest phase of work. So far, a single lock at Great Falls was finished, while another had been almost entirely excavated, but the work on the remaining three had not begun. A team of at most 35 people cut 800 cu yd of rock out of the landscape in four months that spring. Small, black-powder explosions helped the team with its work, just as it had earlier in construction when crews hit stone while digging.

By the end of 1801, all excavation and wall building for the Great Falls staircase locks were done. The workers created the locks from various types of stone on site: red Seneca sandstone (lock 1), a combination of red Seneca sandstone and local rock (lock 2), and “rough-cut native stone” (lock 3). The walls and bottoms of locks 4 and 5, however, were made entirely from native stone as they had been blasted into the bedrock itself, according to The Patowmack Canal at Great Falls Virginia, a trail guide published in 1985 by the Parks and History Association.

A photograph of Great Falls with its rushing water and rocky formations. Trees can be seen in the background.
The most ambitious portions of the Patowmack Canal system were the bypass canal and five locks built at Great Falls (shown here) to aid transport along the river. (Photograph courtesy of Murphy)

Navigating the locks was relatively simple. Locks 1 and 2 were separated by a short channel. However, for locks 3-5, the closure of one gate served as the opening of the next. One drawback of this linked, gated system was water loss, “especially for watercraft travelling upstream,” writes Richard J. Dent in the article, “On the Archaeology of Early Canals: Research on the Patowmack Canal in Great Falls, Virginia.” To offset the water loss, workers constructed a holding reservoir nearby that emptied directly into lock 3, thus ensuring there was enough water on hand for locks 3-5 (Historical Archaeology, Vol. 20, No. 1, 1986).

With the final gates hung in February 1802, the Great Falls Canal and Locks were complete, as was all the Patowmack Co.’s work. In its final form, the Great Falls canal was 1,200 yd long, 6 ft deep, and 25 ft wide at the top, tapering to 20 ft wide at the bottom. The five locks, compensating for a nearly 80 ft elevation drop (locks 4 and 5 alone accomplished about half the elevation change, with each managing 18 ft of lift), were all the same length and width: 100 ft long and 12 ft wide, “except the uppermost lock (No. 1) which was 14 feet wide,” according to Ricardo Torres-Reyes in a report for the National Park Service, “Potowmack Company Canal and Locks: Historic Structures Report, Great Falls, Virginia,” (Office of Archeology and Historic Preservation, May 1, 1970).

Everything from tobacco to flour to hardware traveled the modified Potomac, with merchants paying tolls to the company along the way. By 1807, the company had spent more than $444,500 on initial construction and repairs, over twice the estimated cost. Annual maintenance expenses alone fell short of all tolls collected in the best of years — to say nothing of dividends the project was supposed to pay.

As part of cost-saving measures in its final years, the company abandoned expansion plans, so the dream of connecting the Potomac to the Ohio River never materialized. The directors tried implementing lotteries as fundraisers, but ultimately, after a series of setbacks, the company surrendered its charters in 1828.

Despite disappointments, the engineering the Patowmack Co. organized was impressive. For the first time in the fledgling country’s history, workers used black powder not for war but to blast rock, according to information on the canal published by the National Park Service.

Company failures provided lessons for future projects on how to build in the brand-new nation. Political lessons were learned as well. Although lobbying the Maryland and Virginia state legislatures had its merits, it is not unreasonable to believe that federal oversight in the form of funding would have proved useful and would have helped “coordinate and lead state support,” writes Littlefield in Business History Review. This likely explains why the later Chesapeake and Ohio Canal Co. lobbied Congress for project support.

A plaque denoting the historic civil engineering landmark status of the Great Falls Canals and Locks.
The Great Falls Canal and Locks National Historic Civil Engineering Landmark plaque is mounted on a rock face above lock 1. (Photograph courtesy of Bernie Dennis)

The Potomac River modifications were an ambitious approach to transportation in the U.S. The Patowmack Co.’s “plan expressed an early belief in the potential for expanding American commerce and transportation beyond local areas and coastal ports,” says Littlefield in Business History Review. For a new country, even a failed attempt at interconnection set an important precedent.

In 1969, ASCE designated the Great Falls Canal and Locks as a National Historic Civil Engineering Landmark.

Leslie Nemo is a journalist based in Brooklyn, New York, who writes about science, culture, and the environment.

This article first appeared in the September/October 2023 print issue of Civil Engineering as “A Canal Older Than the Country.”