On June 13, 1886, a log jam developed in the St. Croix River, close to Taylors Falls, Minnesota, and St. Croix Falls, Wisconsin. The river was used to transport large quantities of logs from the forests upstream to the sawmills, and log jams disrupted this business. The 1886 jam was described at the time by a local journalist as "the jammedest jam" he had encountered, and was very difficult to clear, with hundreds of men working for six weeks to clear it, eventually using steamboats and dynamite. The jam was also a major tourist attraction, with thousands of spectators every day. After the jam was broken up in July, cleanup work to remove the logs on the river banks continued until September.

A log jam is a naturally occurring phenomenon characterized by a dense accumulation of tree trunks and pieces of large wood across a vast section of a river, stream, or lake. Log jams in rivers and streams often span the entirety of the water's surface from bank to bank. Log jams form when trees floating in the water become entangled with other trees floating in the water or become snagged on rocks, large woody debris, or other objects anchored underwater. They can build up slowly over months or years, or they can happen instantaneously when large numbers of trees are swept into the water after natural disasters. A notable example caused by a natural disaster is the log jam that occurred in Spirit Lake following a landslide triggered by the eruption of Mount St. Helens. Until they are dismantled by natural causes or humans, log jams can grow quickly, as more wood arriving from upstream becomes entangled in the mass. Log jams can persist for many decades, as is the case with the log jam in Spirit Lake.