Canal instincts: George Washington once dreamed of turning America into a new Venice.

Contemporary presidents come to be judged in broad strokes, though different partisans have different brushes--George W. Bush as moral and resolute, or as dogmatic and incurious; Bill Clinton as immoral, or as caring. Comparable contemporary disputes are more a kind of background noise when we measure those we know only from history books and biographies. They settle in our minds for an attribute or two that fit together, though sometimes we acknowledge the complexities or contradictions in a slaveholding Thomas Jefferson proclaiming the equality of man or an experimental Franklin Roosevelt, committed not to any fixed principle (except perhaps a healthy skepticism toward his own class), but to finding solutions from all kinds of sources.

George Washington has been the subject of less recent historical redefinition than his contemporaries Thomas Jefferson and John Adams, or his latter-day successors Dwight Eisenhower or Harry Truman. For years, Washington has been depicted, almost uniformly, as sober, brave, and dedicated, as a gentleman concerned with maintaining a good reputation, as perhaps a bit fussy, but above all, as virtuous. And perhaps a little dull.

In his new book, The Grand Idea: George Washington's Potomac and the Race to the West, Washington Post writer Joel Achenbach does not upset those impressions. His Washington is as serious as the man described in Douglas Southall Freeman's acclaimed 1948 biography, or in the historian James Thomas Flexner's admiring four-volume series on the first president. Achenbach acknowledges that his book tells a story that has been recounted by other scholars. But this book reveals a dimension of the man not often seen--that of Washington as a dreamer. The retired general imagined and then traced a route west to bind the Appalachian wilderness to the coastal states even before the 13 former colonies were themselves bound to one another.

The route Washington thought could connect the coast to the West was the Potomac River, whose headwaters, at least on a map, were not out of reach of the tributaries of the Ohio River. Achenbach is at his best in communicating to an age of interstate highway drivers why water was the only way for people to go any distance at all in the 18th century. "Roads in America were often hardly more than trails, choked with stumps," he writes. "Throughout the United States, bridges over major rivers simply didn't exist." In the back country, where Washington journeyed in 1784, it was worse. A typical road "did not have a uniform surface. Often it was just a tunnel in the vegetation. A traveler endured diabolical combinations of holes, mires and tree stumps. When a state government got around to chartering a road, it would specify how high the stumps could be. The more a road was traveled by horses and wagons, the more the surface became chewed up and rutted ... Roads were not self-healing, and eventually, the track through the woods would not really be a road at all, just a linear bog."

"In optimistic moments," Achenbach writes, "the general could imagine that, someday, a person would be able to go almost anywhere by water. Canals would lace the landscape, connecting navigable rivers, linking every state, city and village." In a letter to a friend, Washington imagined that someday, with enough effort, it might be possible to bring water navigation "to almost every man's door."

North and South, the Atlantic Ocean connected the 13 states, but East and West, long before the invention of dynamite, the mountains barred the way--except where the rivers cut through. The future president set his sights on exploring the Potomac. Washington had traveled the upper reaches of the river during his youth as a surveyor and a soldier in the French and Indian War. He had later bought many tracts of Western land, some close to the Potomac, others even further away from Mount Vernon.

In September 1784, Washington set out from Mount Vernon on what became a 34-day, 680-mile journey west, in part to collect overdue rents from his tenants in Maryland and Pennsylvania. He also undertook the trip to confirm his romantic belief that the Potomac could be made navigable not just by canoes, but also by boats that could carry goods, and that a suitable road could connect it to some equally navigable river leading to the Ohio.

But there was nothing romantic about the journey. Here is Achenbach's description, based on Washington's diary, of one day's ride: "Dawn to dusk, 35 miles on horrible roads in a still-pounding rain, the brush threatening to swallow them at every, turn. They rode from the North Branch of the Potomac on a generally southeast trajectory, up and across one mountain, and down a 'very steep and bad' road to a major Potomac tributary called Patterson's Creek. They crossed that creek, then another creek, then climbed another mountain."

The book explains why the Potomac idea failed in the long run, despite Washington's intense and successful efforts to bring Maryland and Virginia together to support and help finance a company to improve the river.

Ultimately, the program never worked because the Potomac, though made navigable for small boats for some 200 miles, was too shallow and unpredictable a river for steady, larger-scale transport. Moreover, neither of the ports downstream, Georgetown and Alexandria, offered a harbor good enough to compete with Baltimore's. Finally, in the 1820s, industrialists built the Baltimore and Ohio Railroad to carry freight from the coast to the interior. Rails, unlike water, could flow uphill.

Achenbach often rambles, as when he retells the familiar story. of Washington's reluctance to be president. The prose is sometimes overwrought, and at times, the writing is chatty verging on silly, as when he calls the Jeffersonian ideal of a small central government "a Morn and Pop business" and a "fruit-stand government."

Yet, Achenbach does illuminate a new side of Washington's character. He offers a telling insight when comparing Washington with Jefferson. While Jefferson had never personally traveled across the mountains, he had endless faith in the farmers who settled beyond, and as president he expanded the nation on a continental scale with the Louisiana Purchase. On the other hand, Washington was an experienced traveler who had seen the frontier firsthand yet, as Achenbach writes, remained aloof on his journeys: "When the general moved among frontier folk, he didn't mix. He passed over these people like a dark nimbus cloud. He once referred to ordinary farmers as 'the grazing multitude.'"

Achenbach points up the contradiction between the dreamy Washington and the world-weary one when he annotates Washington's diary entry upon completing his 1784 journey: "The more the Navigation of Potomac is investigated, & duly considered,' said the man who had seen almost nothing but rapids, rocks, low-life squatters, land-jobbers, speculators, broken-down taverns, boggy roads, gloomy forests and nearly impossible portages, "the greater the advantages arising from them appear.'"

Readers come away with a more affectionate notion of a man whose paramount sense of duty enabled both the Revolution and the Republic that followed to succeed. He may not have been as exciting a figure as Jefferson or Adams, Patrick Henry or Tom Paine, but he too had dreams, and happily for readers, Achenbach rediscovers them.

Adam Clymer, political director of the National Annenberg Election survey, retired last summer as Washington correspondent for The New York Times.