On the evening of July 18, 1853 three drunken sand scow workers set out for a trip on the upper Niagara River in a small boat. They ended up in the American rapids, and the boat was swamped. Two of the men were immediately swept to their deaths over the falls, but the third, Joseph Avery, held on. Attempts to rescue him are accurately described in the poem. Avery was swept over the falls around 6 p.m. on July 19, 1853.
For more on Joseph Avery see T.W. Kriner Journeys to the Brink of Doom: True Stories of Disaster, Mystery, and Heroism at Niagara Falls. Buffalo: J & J Publishing, 1997.
See the poem Avery, 1853 by William Dean Howells