The Sultana – Part 5: What caused the Sultana disaster?

The explosion and resulting fire aboard the Sultana that occurred on April 27, 1865 remains the largest maritime disaster in U.S. History. We should honor the memory of those 1,700 plus lives lost.

The boilers on the Sultana were less than three years old, but were in horrible condition. The iron plates were burnt, one of the boilers had two repairs in two months and had already been re-tubed once. Although the inspection 15 days before the explosion indicated they were safe, they were not.

There were three primary reasons for the condition of the boilers and it was the combination of these that was the root cause of the tragedy.

  • Material of Construction – The iron (Charcoal Hammered No. 1) used in construction was a poor quality iron. While it was the best available material of the day, it was not a suitable boiler material. This type of iron gets brittle when it is overheated and cooled repeatedly. By the late 1800’s, the textbooks noted that CH No. 1 iron was “not a suitable iron for boiler construction.”
  • Water Treatment – These boilers had no water treatment and used water straight from the Mississippi River. The mud in the water settled on the plates and surfaces acting as an insulator between the water and the iron. This caused the iron to repeatedly overheat and burn. As noted, this iron gets brittle when it is overheated and cooled repeatedly.
  • Boiler Design – The Sultana Boilers were a firetube design. They used 24 smaller flues instead of the traditional two larger flue design. This larger number of smaller tubes arranged closely together made the boilers hard to clean exacerbating the Mississippi River mud settling on the boiler bottom. This design proved to be incompatible with the material of construction and the water quality and these boiler designs were removed from the Mississippi river.

These points are supported by the testimony while accounting for what engineers did not know about explosions at the time. They match the statistics of boiler explosions of the time and the science of boiler explosion theory. These boilers were almost destined to explode and unfortunately, the boat was packed with those doomed passengers when they finally did.

The modern day benefit to this disaster is the inspection and insurance industry as well as codes such as the ASME Boiler and Pressure Vessel Code and the National Board Inspection Code.


© 2016 The Hartford Steam Boiler Inspection and Insurance Company. All rights reserved. This article is intended for information purposes only.

Patrick Jennings

Pat is the go-to engineer for boilers at HSB. He has been crawling around, studying, talking and writing about boilers for almost 30 years.


  • Thank you, Pat, for this reminder on the 151st anniversary of the disaster and for all the work you have done to help determine the most definitive cause of the explosion aboard the Sultana. Also, thank you and all of the folks at HSB for your excellent and ongoing work and dedication protecting lives and property around the world. Sincerely, Mike Marshall, Producer, “Remember the Sultana” documentary

  • Thank you for these fascinating and well-researched blog posts. I am researching an early employee of HSB, Curtis Crane Gardiner, a Civil War veteran who worked in the St. Louis office of HSB in the 1860s. I wonder whether HSB has an archive that might help me determine exactly when and in what capacity Col. C.C. Gardiner began his work for HSB in St. Louis. I would greatly appreciate any information you may offer.

  • A great series of blogs Patrick – Many thanks.
    Even where water quality was ‘better’, and inspections commonplace, it was the experience of the Royal Insurance company that many ‘Yorkshire’ boilers were failing catastrophically for no readily apparent reason. This lead to the establishment of Laboratories (sadly since closed) by Royal to investigate the cause and lead the way in looking at the structure and materials concerned in failed boilers. The observation of ‘beachmarks’ on failed plates lead to a better understanding of fatigue failures within boilers, and the introduction of pressure testing as a more routine method of ensuring safe operation. I sincerely hope that the records were preserved in Manchester, as they allowed a fascinating insight of engineers shining a light into the dark corners of materials science in the 19th century.

  • Hi! I just wish to give you a big thumbs up for your excellent info you’ve got here on this post. I am returning to your blog for more soon.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.