Boiler explosions, lightning strikes and accidents also sunk many a steamboat. One of the grander ones, the Montana, turned up this fall on the Missouri River near St. Charles. The elaborate steamer was as long as a football field with lavish touches aimed at pleasing its mostly wealthy clientele. It went to its watery grave after striking a tree below the surface in 1884.
The U.S. Coast Guard and Army Corps of Engineers urge sightseers to stay away from any shipwreck sites. Sandbars leading to them can be unstable and dangerous, and the rusted hulks can pose dangers for those sifting through them.
Plus, taking anything from them is illegal. By law, sunken ships and their goods belong to the state where they went down.
While unusual, it's not unprecedented for low water levels to reveal historic artifacts.
Last year, an officer who patrols an East Texas lake discovered a piece of the space shuttle Columbia, which broke apart and burned on re-entry in 2003, killing all seven astronauts aboard. And the remains of a wooden steamer built 125 years ago recently were uncovered in a Michigan waterway because of low levels in the Great Lakes.
But treasure hunters expecting to find Titanic-like souvenirs in rivers will likely be disappointed if they risk exploring the lost boats.
"It's not like these wrecks are full of bottles, dishes, things like that," said Mark Wagner, an archaeologist at Southern Illinois University-Carbondale. "If there was anything on there in the first place, the river current pretty much stripped things out of these wrecks."
Such was the case with the USS Inaugural, a World War II minesweeper that for years served as a docked museum on the Mississippi River at St. Louis. The Great Flood of 1993 ripped the Inaugural from its mooring near the Gateway Arch. It crashed into the Poplar Street bridge, and then sank.
In September, the rusted Inaugural became visible again, though now nothing more than an empty, orange-rusted hulk lying on its side not far from a south St. Louis casino.