[TXnMA]

Hmm... Sultana? Mississippi riverboat, end of Civil War, overloaded with freed Union POWs, sloppy boiler repairs at Vicksburg, boilers exploded somewhere upstream of Vicksburg, news swamped by news of Lincoln's assassination.

Largest maritime loss of life in the US?

For more detail than that, I'd have to look it up...

[PeteB570]

And in the “Mass Killings” category there is always the Bath School Bombing from 1927.