E.M. Cassaday is credited with completing the first producing, drilled well west of the Mississippi River in 1862. This initial shallow well located near oil seeps six miles north of Canon City, Colorado, is considered to be the start of the Florence Field. Cassaday's operation included a crude distillation process to produce wagon grease and lamp fuel. Thus started the first major petroleum refining center in the west which lasted until the 1936 shut down of the last refinery in Florence, Colorado. In 1876 the first well near Florence started a major exploration effort that eventually defined the limits of the field. More than 15 million barrels of oil have been produced from a total of more than 1200 wells. Stripper production continues from wells that include several original wood beam pumpjacks.
Geologically the field is noteworthy because 1) the oil is produced from a syncline rather than the traditional anticline and 2) the oil is produced from fractures in the Pierre Shale rather than the typical high permeability reservoir rock found in early oil fields. The oil moves into the fractures by gravity with subsequent drainage into well bores where it is pumped to the surface.
The discovery of major reserves lead to many investment schemes
involving land, oil, and refining. The first refinery was built
by Arkansas Valley Oil and Land Company near Florence. Eventually
major refineries were built by United Oil Company, Standard Oil
Company and Continental Oil Company. As production dwindled and
refineries suffered major fires and explosions, they successively
were closed