In the mid-1830s logging began in Michigan and grew into a significant industry. Michigan was extensively logged for the Eastern white pine, measuring tall and exceeding in diameter, along with the hardwood forests. By 1854, sixteen sawmills were in operation, producing over of lumber. These operations left behind branches, bark and quantities of unused wood. The fires of October 8, 1871, started after a long dry summer. Most areas had had no rain in months, making the dried-up vegetation and logging debris, known as "slash", fuel for the fires. These fires were the result of hundreds of smaller land-clearing fires whipped together to form a massive wall of flames by gale force winds.
Consequences
In addition to the fires originating in Michigan, the Peshtigo firestorm in Wisconsin crossed the Menominee River and burned in Menominee County, Michigan. More than were burned in Michigan, including the Menominee County area. Not only was the land burnt and left barren, thousands of buildings were destroyed with no lumber left to rebuild. Hundreds of families were left homeless. The extent of property loss, animal deaths, and forest devastation has never been determined. Also unknown is the total number of human deaths. Some estimates put the loss of life at fewer than 500, but they were largely based on families reporting their members missing. In 1871 in Michigan there were hundreds to thousands of lumberjacks and salesmen spread out across the state, along with settlers in remote areas, making it impossible to total the loss. Because the Michigan fires occurred during the day, the estimate of the death toll is lower than the Great Chicago Fire's estimated 250-300 dead.
Comet hypothesis
One speculation, first suggested in 1883, is that the simultaneous fires across the Midwest were caused by the impact of fragments from Comet Biela. The theory was revived in a 1985 book and investigated in a 2004 paper to the American Institute of Aeronautics and Astronautics. The key hypothesis is that methane from the comet provided the fuel for fires across the region to flare out of control. Others dispute this theory, arguing that meteorites in fact are cold to the touch when they reach the Earth's surface, and there are no credible reports of any fire anywhere having been started by a meteorite. Various aspects of the behaviors of the Chicago and Peshtigo fires attributed to extraterrestrial intervention have more mundane explanations. No external source of ignition was needed; numerous small fires were already burning in the area after a tinder-dry summer and all that was needed to generate the massive blazes in the Midwest were the winds from the front that moved in that evening.
