Samuel Clemens drew his pen name from a depth sounding called by crewmen on the riverboats he piloted on the Mississippi River — “by the mark twain” — which meant the depth of the river was two fathoms, or 12 feet, the minimum depth for safety for steamboats of the time.

Those soundings were made by men tossing a weighted, knotted rope over the prow and counting the number of knots that went under water. If two knots went under, then the lineman called “by the mark twain,” which I’m sure was music to a pilot’s ears as he tried to guide his boat up or down a river with an ever changing bottom.

That river was the main north-south highway for the North American continent long before Clemens, who was more famously known as the author Mark Twain, was born, and long before European man ever saw the stream, in fact.

Twain, a Missouri native, never forgot his time on the Mississippi River and some of his most popular books, “The Adventures of Tom Sawyer,” “The Adventures of Huckleberry Finn” and “Life on the Mississippi” to name three, drew directly from his familiarity with the river.

During Twain’s day, the Mississippi River and the rivers that ran into it were the nation’s interstate system. The main mode of transportation on the Mississippi and the other rivers was the steamboat, mostly steamboats driven by paddle wheels. Many of those boats carried both passengers and cargo from town to town on the rivers. The large towns of those days were located on rivers because of the relative ease of transportation, especially of cargo, along these watery highways.

Cargo still sails up and down the Mississippi River and along other streams, including the Tennessee-Tombigbee system that cuts through the northeastern part of the state while the Mississippi marks most of the western boundary of the state. Steamboats, the classic ones, though, are now a thing of the past and passengers no longer travel the Mississippi River.

The Delta Queen, which used to carry passengers up and down the Mississippi, ended her passenger runs on Oct. 31 of last year in Memphis, Tenn. This proud, glorious queen is now tied to the shore in Chattanooga, Tenn., where she is expected to become a hotel. The Delta Queen’s exemption, and those of her sister steamboats, from the federal Safety at Sea Act ended on that date.

What a sad and dismal end for an era that inspired such vibrant literature as that written by Twain and other, lesser-known, writers. Now the river has become simply a highway for commerce, those strings of barges pushed up and down the river by tugboats.

A few years back, some enterprising entrepreneur came up with the idea of moving passengers up and down the river on barges pushed by a tugboat, but I don’t know whatever happened to that idea. I haven’t heard of such trips on the Mississippi River since before Hurricane Katrina. Perhaps such accommodations didn’t draw tourists with romantic dreams of traveling the river the way the Delta Queen and other paddlewheelers drew them.

What a sad ending for a once proud queen that carried passengers from Cincinnati to New Orleans and points in between during the last 50 years. Most of her recent runs were between New Orleans and Memphis, but since her arrival on the Mississippi River from her origins in California, she had become a landmark that Mississippi River towns, many of which depended in part on the tourists she ferried up and down the river, looked forward to. Her future existence may be guaranteed by her inclusion on the National Historic Register, though her sailing days are over.

My sister Mary owns a bookstore in Natchez and said the days that the Delta Queen landed were good days for her store. Other shop owners and restaurant owners both “Under the Hill” and above on the high bluffs looked forward to the Delta Queen’s landings with her calliope, a steam organ, announcing her arrival. With her forced “retirement,” that source of tourists is now gone from this historic city and others like it along the river that was once as crowded with river boats as today’s interstates are crowded with automobiles.

No longer can we dream of one day traveling in Mark Twain’s “footsteps” by taking a trip on a riverboat driven by paddle wheels on the Mississippi River. When a person grows up looking out over the wide Mississippi from the bluffs of Natchez and reading Mark Twain’s books, as I did, such dreams come naturally. I never traveled on one of the boats, simply because it was so costly, but I sure could dream about it, and the sight of the occasional paddlewheeler coming into port or passing by on the river gave substance to the dreams.

Today, anyone having such dreams will have to come to them only by looking out over the river and through the literature of Twain and others. Somehow, I seriously doubt that spending the night on a boat tied to a dock will have the same meaning as traveling the river on such a proud and glorious queen.