The incongruity of it all still leaves me a little dazed.

We were aboard the delightful Delta Queen, an authentic river steamboat, cruising the lower Mississippi for three days, a journey very much out of another era. We were bound, like the famed paddle-wheelers of the past, for a pair of river plantations, once bustling but now dozing in retirement. Tunes from the steam calliope danced in my ears, and a copy of Mark Twain's river adventures rested in my lap.

The Delta Queen carried about 180 passengers, its capacity, and at least some of us pictured ourselves as 19th-century travelers in the golden age of steamboats. Our romantic ports of call, and a fair portion of the lush Louisiana countryside through which we passed, helped foster that illusion. But our antique -- though still quite plucky -- conveyance kept nosing forward into the 20th and sometimes, it seemed, into a surreal 21st century. We were in a time warp.

That murky Old Man River keeps rolling along, in song and in fact, but there have been a lot of changes on shore. Twain's eye, when he was training to become a riverboat pilot, surely must have caught broad sweeps of forest and farmland and mile after mile of flourishing sugar cane and cotton. Upriver out of New Orleans, we found ourselves gliding in historic elegance past long stretches of modern, heavily industrial America.

This part of the Mississippi River is hard-working. Its strong current is crowded with oceangoing freighters and oil tankers as far north as Baton Rouge, and the banksare dotted with oil refineries, chemical factories, grain elevators and giant power plants. By day, they are grotesquely ugly, a huge jumble of shafts, tanks, towers and chimneys. But lighted at night, when we did much of our sailing, they become an almost magical fantasyland off in the distance. I easily skipped the bingo and the bluegrass concert in the lounge to sit on deck and watch the grand show passing by.

Sometimes we seemed to be paddling through a twinkling city of Oz, where thousands of brilliant white lights adorning these structures gave the look of diamonds rather than emeralds. In another moment, though, the scene might take on the horrific look of London during the Blitz. Chimneys belched flames, lighting the sky, and clouds of white smoke billowed from a dozen sources as if a rain of bombs had just poured upon the shoreline. Or, around the next bend, an array of giant mechanical cranes, aglow in bright spotlights, easily began to resemble giant robots in harsh command of a future world.

And then the calliope would begin to play, or I'd catch a glimpse of the Delta Queen's big red paddle wheel biting deep into the river, or the boat -- not a "ship," insists Capt. Gabriel Chengery -- would toot its friendly steam whistle at a passing barge, and we would drop back into the 19th century again. As I said, it was a bit difficult keeping one's perspective on this trip.

The Mississippi is both this country's longest river and, as Mark Twain points out in "Life on the Mississippi," "the crookedest river in the world." Measuring from the headwaters of the Missouri River, a major tributary, the Mississippi winds almost 4,000 miles to the Gulf of Mexico. Its flow is maintained by runoff from 31 states and two Canadian provinces. "It is not a commonplace river," to quote Twain again, "but on the contrary is in all ways remarkable."

Traveling these endless twists at a rate of from 6 mph to a peak of 12 (riverboats don't calculate speed in knots), we covered only a tiny portion of this great distance -- a mere 170 miles north from New Orleans to St. Francisville, La., and then back again. But our three-day cruise, one of the shortest on the Delta Queen's 10-month itinerary, proved just enough to give us a satisfactory glimpse of the life and lore of the river.

In the heyday of paddle-wheel travel, before the Civil War, more than 11,000 steamboats -- many of them floating palaces like the Delta Queen -- plied the Mississippi and its branches, carrying cargo and passengers to many of the major cities of the country's heartland: Natchez, Memphis, St. Louis, St. Paul, Cincinnati, Pittsburgh, Nashville and Chattanooga. Now only the 61-year-old Delta Queen, a historic treasure, and two modern versions, the Mississippi Queen and the New Orleans, offer overnight passage to these ports -- and only the first two really are steamboats.

Followingthe Civil War, the paddle-wheelers gave way to America's growing railways and to the impertinent little tugboats that could haul greater loads more cheaply in long convoys of barges. I saw single tugs a quarter the size of the Delta Queen moving as many as 20 grain and coal barges, marshaled four abreast and five deep. Jonathan Raban, an acclaimed British writer who navigated the length of the Mississippi in a small motorboat and wrote about it in 1982 in "Old Glory: An American Voyage," lived in constant fear that one of these cumbersome behemoths would run him down and not even know it.

In the old days, too, a river journey was a tricky thing, and accidents were frighteningly common. The fast-flowing Mississippi had a way of cutting new channels overnight or depositing a sandbar where boat captains and their pilots counted on deep water. Time and again, the river beached unwary boats or destroyed them completely. Today, the river has been tamed with dams and levees, if not always kept under control, but piloting a paddle-wheeler -- or a tugboat convoy -- still calls for a close watch on the caprices of the current.

Twain's adventures and misadventures had given me an unsettling awareness of the dangers of early river travel. A tour of the Delta Queen's pilothouse was therefore reassuring. Today's riverboats use radar to detect the traffic ahead at night or in a rainstorm and to spot any partially submerged log that could splinter the boat's wood paddle wheel and disable it temporarily. And there's sonar to keep the duty officers informed of the river's depth. Nevertheless, the Mississippi Queen did collide with a barge a few years back. There were no injuries, but the boat was laid up for several weeks for repairs.

Once riverboats tooted their whistles to signal each other. The Delta Queen still does, but that's really just to please passengers like me, who have read Twain and hope that life on the Mississippi has not changed so very much. Now, though, essential communication between tugboats, freighters and other craft is handled by radio. Often, however, I noticed a passing tug would send up several loud blasts. That, it turns out, was just a friendly "hello." The river people, says the captain, are very fond of the old Queen.

Like any landlubber, I thought all boats heading upriver kept to the right and those coming down kept to the left -- just like traffic on a busy interstate. Not so, I learned in the pilothouse. On the way upstream, a boat may cling to either shoreline to avoid the middle of the river, where the current is strongest. Coming downstream, the pilots prefer to ride the current for more speed. Because a boat in the current is harder to handle, it gets the right of way -- and the choice of whether to pass on the left or right. On the busy Mississippi, the radio crackles nonstop relaying these messages.

Has this technology stripped all romance from the piloting of a paddle-wheeler? I wondered. Would anything seem familiar to Twain? Perhaps one maneuver would. On our first night out, well after midnight, Capt. Chengery, who had gotten ahead of schedule on our itinerary, decided to "choke a stump" until dawn. It sounds ominous, but it means only that along a woodsy section of the river the Delta Queen -- all 1,600 tons of it -- nudged close to a sandy bank and tied up like any rowboat to the nearest strong tree.

Our mid-November voyage got underway gloriously with a gala, unscheduled duel of the calliopes, as rousing a send-off as any river traveler could hope for. To the piping chorus of "way down yonder in New Orleans," the Delta Queen pulled away from the New Orleans dock promptly at 7 p.m., followed closely by its sister ship, the Mississippi Queen -- both looking like giant, white-frosted wedding cakes ablaze in starry lights.

Though each had its own upriver itinerary, the two boats paraded together in full glory past the New Orleans skyline, past famed Canal Street and the wonderful Old French Quarter, their calliopes singing out loudly across the water. Then out from shore came the Natchez, yet another huge paddle-wheeler, this one in the humbler trade of harbor sightseeing tours. But its calliope sang just as strongly.

The only clear winners in this musical competition, as one calliope tried to out-toot the other, were the passengers, who sang and applauded until the lights of the city disappeared far behind. If this was "steamboatin' " -- the Delta Queen drops the "g" in a gesture to the local accent -- then it was going to be fun. Then we stepped down into the dining room for a tasty dinner of fresh Louisiana catfish, lightly seasoned with local Cajun spices -- yet another splendidly appropriate send-off.

The name "Delta Queen" not unreasonably leads one to believe that it is Queen of the Mississippi Delta, but that is not the case. The historic boat was built in 1926 to operate on the Sacramento River, making overnight trips between San Francisco and the California state capital at Sacramento. Unaware of the approaching stock market crash of 1929, the owners appointed the boat's four decks with polished brass and rich oak, teak, mahogany and Oregon cedar -- fine woodworking that remains.

But the Depression doomed the luxury river trade, and the Delta Queen was taken out of overnight packet service and languished for several years. The Navy drafted it in World War II, painted it government gray and put it to useful defense work in San Francisco Bay as a floating barracks and a troop ferry. In 1945, it carried delegates to the founding conference on the United Nations on sightseeing tours of the Bay.

In 1946, a predecessor of the Delta Queen Steamboat Co. bought the Delta Queen at auction and had it towed 5,000 miles from San Francisco through the Panama Canal to New Orleans. This was a journey of some peril, since flat-bottomed riverboats such as the Delta Queen can be torn apart by high ocean waves. But it arrived in New Orleans safely, and from there, it paddled on its own steam to Pittsburgh to be refitted for Mississippi and Ohio river cruises. The Delta Queen was back in the river trade.

Though now it is regarded as America's only authentic overnight paddle-wheeler -- the other two overnight packets were built to modern specifications -- the years have not been all smooth sailing for the Delta Queen. An ongoing concern is the boat's wooden superstructure. The Safety at Sea Law bans such use of wood on vessels because of the fire potential. But the Delta Queen so far has been able to win a series of congressional exemptions, which must be reapplied for every five years. To qualify, it is kept painted with fire-resistant paint, and a sensitive system of smoke detectors and sprinklers has been installed in the cabins and public rooms.

What a loss it would be if some day the Delta Queen was taken off the river. Its fine wood and shiny brass give it a stately elegance that its sister ship, all glass and metal, just can't duplicate. If I were looking for comfort, I'd book a roomy cabin on the Mississippi Queen. To relive the steamboatin' days of Mark Twain -- did his cabin have bunk beds as ours did? -- the only choice is the Delta Queen.

There are far lovelier sections of the river to cruise than our route from New Orleans past Baton Rouge to St. Francisville, a mostly flat landscape partially hidden by the high levees built to keep the Mississippi within its banks. Capt. Chengery, who started out as a night watchman on the Delta Queen 20 years ago, favors the trip on the Ohio between Cincinnati and Pittsburgh because of the scenic high bluffs and the many river towns that can easily be seen from the deck.

On the other hand, I was kept diverted by the amazing volume of traffic on the river. We seldom were out of sight of a huge freighter or barge convoy. If the calliope was playing, you might spy a foreign crewman dancing a quickstep to an old river tune. Many had their cameras out snapping away at this rare curiosity from another time.

Oceangoing vessels can sail as far north as Baton Rouge, the Louisiana capital, and might proceed farther were it not for a low bridge across the Mississippi built in the late 1930s. It is said that Huey P. Long, the state's famous governor and senator, chose the height deliberately so that Louisiana could keep all the freighter trade to itself rather than lose some of it to other ports upriver.

Mileage indicators pop up regularly on the shore, visible with a pair of binoculars. So at any time, I had no trouble telling how far we had come. In the gift shop, I bought a copy of "Steamboatin' Log" by Bern Keating, a mile-by-mile description of important sites along the way. I kept it in hand as a road map to the past I was intent on viewing.

We'd started at Mile 95 in New Orleans. At Mile 234, the guidebook informed me, we were passing what is probably the largest oil refinery in the world, an Exxon plant fully 11 square miles in size and spouting all kinds of smoke and vapors. We couldn't scoot by fast enough to suit me. Mile 249 was the site of one of the river's worst tragedies. In the 1830s, a riverboat carrying 700 Cree Indians forced from their homeland to Indian Territory in Oklahoma collided with another vessel. More than 400 people were killed.

A riverboat the size of the Delta Queen -- it is 285 feet long, almost the length of a football field -- rides the river quite smoothly and quietly. We skimmed along as though skating on unriffled ice, no dips or leans to send you wobbling off balance. The paddle wheel splashes softly, but otherwise you are mostly unaware of the engine. The only noise to interrupt a nap is a blast from the whistle.

We stopped for several hours at two plantation homes. The first, at Mile 170, was Houmas House, a Greek revival mansion named for the local Indians who once owned the land. Completed in 1840, for a time it looked out over 20,000 acres of sugar cane. It is still surrounded by large gardens. Once it had a view down an avenue of live oaks of the river. But as at other plantations in this area, the river is now hidden behind the flood levees.

Our most distant point north, at Mile 265, was the charming rural village of St. Francisville, home to a remarkable collection of pre-Civil War buildings, many fully restored, and Rosedown Plantation, notable for its long avenue of moss-draped live oaks and for its 28-acre formal European garden created after the plantation owners' grand tour of Europe in 1828. The visit to St. Francisville gave us yet another little lesson in the will and way of the Mississippi.

The town -- population of about 1,500 -- sits well back from the river's edge atop a 100-foot-high bluff in the Feliciana Hills, considered high country in Louisiana. A century or so ago another village at the foot of the bluff, Bayou Sara, was destroyed by a flood and was never rebuilt. Today, concrete "mats" are kept there for use in lining the levees when a flood threatens.

This fall, however, the Mississippi water level has been unusually low because of slight rainfall upriver. As a result, the Delta Queen couldn't tie up at its customary landing. Instead, it "choked a stump" again on the far side of the river, and we had to be ferried across to town. On the bank, "Miss Emily," a resident of the area, was waiting with her basket of homemade pecan pralines and roasted peanuts to sell to passengers.

In a way, I was glad for the inconvenience of the ferry. No matter what modern devices the Delta Queen has acquired, the Mississippi is still in command -- just as it was when Mark Twain worked the river.