The Potomac River near Georgetown — endangered by pollution and, obviously, rowers. (Astrid Riecken/FOR THE WASHINGTON POST)

Back to the river: A group called American Rivers puts out an annual list of the most endangered rivers. This year the Potomac tops the list, followed, in order, by the Green, the Chattahoochee, the Missouri, the Hoback, the Grand, the South Fork Skykomish, the Crystal, the Coal and the Kansas.

I like this list a lot because it includes a bunch of rivers I’ve never heard of, and which sound like they’d be fun to raft down. I like the sound of the Hoback. I am happy that there’s a Skykomish with multiple forks. I question whether there’s really such a thing as the Kansas River. I didn’t think they had rivers there, just vast fields of grain and a lot of cows and the occasional tornado that can deposit a house from someplace black-and-white to someplace in color.

That said, there is nothing here that I can see in this American Rivers report that explains why the Potomac is more endangered than any other river in the country. Why are we number one? A Potomac River fact sheet states:

“[T]he Potomac is threatened by agricultural and urban pollution that will only get worse if Congress rolls back national clean water protections. If Congress puts polluters before people, our nation’s river— and many other rivers nationwide— will become a threat to public health, unsafe for drinking water, wildlife, or recreation.”

I have a hunch this most-endangered designation is political at some level, but I don’t want to go out on a limb here.

American Rivers wants people to write to Congress to protest a Republican effort in the House and Senate to change the way the administration is enforcing the Clean Water Act. This Republican effort is merrily named the “Preserve the Waters of the United States Act,” and is listed as S. 2245 and H.R. 4965 for those of you keeping score at home. The Internet provides us with the text of S. 2245, but it’s gibberish to me.

This appears to a protracted struggle between Republicans and the Obama administration over the efforts, and methods, of the E.P.A. to enforce the Clean Water Act. A flashpoint is apparently in Appalachia — roughly in the vicinity of the headwaters of the Potomac, though I don’t know how much mining is still done in the river’s watershed (in the old days, a lot). Just at random, via Google, here’s a news account and here’s another, and here’s one,. (I’m sure there are readers out there who know all about this issue, so please post a comment!)

The Potomac has been in the spotlight before — back when it was so nasty and cruddy that anyone who fell into it was told to get a tetanus shot. Here’s the famous Stewart Udall report from the 1960s called The Nation’s River. It has a nice passage near the beginning about the Potomac:

“In many ways it is a classic Eastern river, copious and scenic, that drains some 15,000 square miles of varied, historic, and often striking landscape, from the green mountains along the Allegheny Front to the sultry lowlands of the estuary’s shores where the earliest plantations were established among the Indian tribes. It has tributaries large and small whose names echo with connotations for American ears--the Shenandoah, the Monocacy, the Saint Mary’s, Antietam Creek, Bull Run....”

It’s been 10 years since I wrote a Washington Post magazine piece on The Potomac [impossible to find on our own website but I found a pirated version at something called] that prefigured my book on George Washington and his Potomac obsession. The river is in many ways a triumph of 1960s and 1970s conservation efforts, helped along by the failure of most of the schemes to turn it into an industrial waterway. It’s arguably a case study in how federal laws and regulations can make a dirty river swimmable (much of the river is protected by federal parkland, notably the C&O Canal park along the Maryland bank, and the G. W. Parkway on the Virginia side).

Just to put it on the record here at WaPo dot com, here’s how — panning back for the big picture — I ended my Potomac story in the magazine:

The river, changed by the Ice Age and the Industrial Age, has been changed again by the Information Age. In the Information Age we are freed from geography. Information travels instantly around the globe. Through e-mail we routinely communicate with people whom we have never seen and whose location may be unknown to us. We surf Web sites located in a place called cyberspace, the ultimate nowheresville.

You have to ask: Does geography matter anymore?

At the very least it no longer shapes us the way it did George Washington and his generation. We aren’t made exceptional by it or rendered isolated by it. What shapes society now is technology. It’s fitting that the Internet was invented at a military think tank on the Potomac.

We live in a time when the very concept of place is in danger of extinction. People are transient. Culture is fluid. Distinctive edges and crags and crannies are gradually eroded by the homogenizing forces of commerce and globalization. More and more places in America could be anywhere: shopping malls, cookie-cutter subdivisions, the faux “town centre.” You don’t talk to your neighbors but exchange e-mails daily with a stranger in Duluth. Our neighborhoods look empty as people stay inside, staring into cyberspace.

The Potomac was once a river so important and alluring that Congress placed the permanent seat of the federal government on its bank. President Washington had the authority to select a spot for the new Federal City anywhere on the Potomac from the Anacostia (aka the Eastern Branch) to Conococheague Creek, more than 100 miles upstream at Williamsport, Md. The spot he chose was a natural crossroads, the intersection of the liquid route to the West and the Post Road (now U.S. Route 1) linking cities along the East Coast. But today all that seems kind of quaint. The situation has largely reversed: The capital is a sprawling city that just happens to have a river running through it.

Many people appreciate the Potomac, but few know it the way Vic Jenkins knew it as a young man, the way George Washington knew it, the way a lockkeeper knew it or a canal boatman or an Indian fishing for sturgeon.

But the river still has an important function. It’s a time tunnel. It’s the Route to the Past. It’s a portal to a moment when the nation was young, when rivers were highways, when water ruled the planet, when omens good and bad hung in the air -- when no one knew how this experiment in self-government called the United States was going to turn out.