Jackass Spring oil seep first created all of the exploration interest in the Shannon and Salt Creek oil fields (see Fig. 1).  Jackass Spring is located in the Northeast 1/4, Southwest 1/4, Section 13, Township 40 North, Range 79 West, Natrona County, Wyoming.  The Shannon pool is located on the northeast flank of the Salt Creek anticline. Samuel Aughey, Territorial Geologist of Wyoming from 1885-1886, who coined names for all of his claims, named it Jackass.

The first man to attempt to acquire land in the Salt Creek area was Representative Stephen W. Downey, a delegate of Albany County (Wyoming).  His first claim was made in 1883 and covered 160 acres of land near the northeast edge of the Salt Creek field and other tracts, one of which contained a prolific oil seep (Jackass Spring).  About 1884, A.T. Seymour took claims on the Shannon field to the north.

In May of 1884, Aughey "jumped" Downey's Jackass Spring claim along with John Bothwell. Before the close of 1892, the team of Aughey and Bothwell and a group of New York men became owners of four quarters of the land, of which the Jackass claim was one. Land was not leased in those days but staked as petroleum placer claims.  By 1892 the “interest” in Salt Creek had considerably widened. By this time the discovery well, the No. 1 Shannon, was completed in March of 1889.  It was drilled to a total depth of about 1,000 feet and was able to produce 5 to 10 barrels of thick paraffin-based oil of about 24 Baume (specific weight of oil). It was located in the Shannon pool north of Jackass Spring oil seep.

One of the most colorful characters to enter the Salt Creek drama was Cy Iba.  He learned prospecting in the California gold fields and brought his talents to Wyoming when he began locating and staking oil claims. He also founded the Casper Mountain Mining District, and it is in his district that the mining ghost towns of Copperopolis and Eadsville are located. Cy staked some 30 claims in Salt Creek and did the required assessment work.  The law required that the assessment work be of the value not less than $100 per claim per year.  The law also stated that a pit must be dug 6 x 8 feet to a depth of 10 feet. This was very easy to do at Salt Creek because of the soft clay (Cody Shale). Two men could do it in a short time of perhaps two hours.

In 1894 a refinery was built in Casper on a small site close to where Center Street crossed the Chicago and Northwestern Railroad tracks.  As of the 4th of April 1895, 60 barrels of refined engine oil had been shipped from the refinery.

The drilling of No. 1 Salt Creek (or No. 1 Dutch) in October 1908 opened Salt Creek as one of the most significant fields in the Rocky Mountains.   The discovery was made in the First Wall Creek (Frontier Formation) sand in Section 23, Township 40 North Range 79 West; the potential was for 150 barrels of oil per day (BOPD). By Dec 31, 1911, Salt Creek had already produced 66,798 BO. In the Great Depression year 1934, the cumulative production rose to 258,722,178 BO. The upper Cretaceous Frontier Formation has been the main productive interval at Salt Creek, having produced in excess of 432,000,000 barrels of oil (as of 1979).   As of 1999, Salt Creek has produced about 675,000,000 BO and 720 billion cubic of gas (data from WOGCC).  Nine zones produce at Salt Creek and from the oldest to the youngest they are: Pennsylvanian Tensleep Sandstone, upper Jurassic Sundance and Morrison Formations, lower Cretaceous Lakota Sandstone and Shale, Lower Cretaceous Third Wall Creek, Second Wall Creek, and First Wall Creek Sandstones, and Upper Cretaceous shales.

In 1923, the North and South Railroad was built from Illco Junction on the Chicago and Northwestern Line just to the northwest of Casper, Wyoming to Salt Creek.  This railroad line was short-lived, as larger pipe lines were used to move the oil rather than using the railroad tank cars. In 1925 Salt Creek became one of the first oil fields in the country to be powered totally by electricity.

The boom days of Salt Creek in the twenties and thirties caused many business buildings to be built in downtown Casper and most of them are still standing today.

As of October 1989, the Salt Creek field has 1,196 wells and the cumulative production is 633,342,574 BO, 711,666,946 thousands of cubic feet of gas (MCFG) (as of December, 1988) and 3,865,237,488 BW. Truly a giant!