Clemens visited the town frequently during his piloting days on the Mississippi River. In June of 1858 he spent a week there while his brother, Henry, was in hospital after the Pennsylvania's explosion.
Mark Twain was again in Memphis in 1882. From Life on the Mississippi:
The boat was to tarry at Memphis till ten the next morning. It is a beautiful city, nobly situated on a commanding bluff overlooking the river. The streets are straight and spacious, though not paved in a way to incite distempered admiration. No, the admiration must be reserved for the town's sewerage system, which is called perfect; a recent reform, however, for it was just the other way, up to a few years ago—a reform resulting from the lesson taught by a desolating visitation of the yellow-fever. In those awful days the people were swept off by hundreds, by thousands; and so great was the reduction caused by flight and by death together, that the population was diminished three-fourths, and so remained for a time. Business stood nearly still, and the streets bore an empty Sunday aspect.