Located along Fourmile Creek (also known as Oil Creek) about six miles north of Cañon City, Oil Spring is a shallow oil seep that was the site of the first commercial oil production in Colorado. Primarily active from 1860 to 1881, the seep produced at most one to three barrels of oil per day. In 1881 interest in the area around Oil Spring led to the discovery of the state’s first major oil field, the nearby Florence Oil Field, which dwarfed Oil Spring in production and effectively ended its viability as a commercial operation.

Prior to white settlement in Colorado, Southern Utes knew of Oil Spring and used the oil seeping out of the ground there as body paint and medicinal ointment. After the Colorado Gold Rush of 1858–59 led to the establishment of Cañon City as a mining supply town, Oil Spring was claimed by Gabriel Bowen in September 1860, one year after the first oil well in the United States was drilled in Pennsylvania. Bowen immediately formed Colorado’s first oil company, G. Bowen & Co.

In the winter of 1860–61, Bowen’s claim was apparently jumped by J. L. Dunn, who dug four pits at the spring. One of the pits produced a barrel per day, but the others yielded little. Dunn left the area in early 1861, after being charged with cattle rustling. Bowen regained control of Oil Spring. He also operated a grain mill farther down Oil Creek from the seep.

In January 1862, Alexander Cassidy bought the Oil Spring claim. That October he and two partners formed the Colorado Oil Company, the state’s first commercially productive oil enterprise. In 1862–63 the company developed the state’s first oil well at the site, but no oil was found deep underground, only near the surface. The seep produced at most a few barrels per day, which the company sold in Cañon City, Denver, and Santa Fé.

Cassidy also tried to interest Eastern investors in developing the seep. In 1865, after buying out his partners, he sold his claim to three men from Boston. They formed the Boston and Colorado Oil Company, hired a superintendent with experience in the Pennsylvania oil fields, and invested heavily in equipment and new wells. Despite their efforts, the seep continued to produce only a few barrels per day, which were sold for lamp, heating, and lubricating oil.

The seep at Oil Spring convinced Cassidy that the area around Cañon City was a promising oil-producing region. He continued to do exploratory drilling on the edge of town. In 1880, Cassidy and Isaac Canfield started drilling a well southeast of Cañon City, supposedly for water, and in January 1881 the well struck oil at a depth of about 1,445 feet. This marked the discovery of the Florence Oil Field, where production peaked in the 1890s at more than 3,000 barrels per day.

After development started in the Florence Oil Field, the low production at Oil Spring ceased to interest most oil companies. Occasional leases and drilling continued at the site into the twentieth century, producing mostly dry wells. Old wells were capped in the early 1990s, but a small amount of oil continues to seep at the site.