Pioneer was the first of three submarines privately developed and paid for by Horace Lawson Hunley, James McClintock, and Baxter Watson.

While the United States Navy was constructing its first submarine, USS Alligator, during the American Civil War in late 1861, the Confederates were doing so as well.

Horace L. Hunley, James McClintock, and Baxter Watson built Pioneer in New Orleans, Louisiana.

[3] Pioneer was tested in February 1862 in the Mississippi River, and later was towed to Lake Pontchartrain for additional trials where it successfully managed to sink a schooner,[4] but the Union advance towards New Orleans the following month prompted the men to abandon development and scuttle Pioneer in the New Basin Canal on 25 April 1862.

The Bayou St. John submarine and Pioneer may have undergone trials at about the same time and confusion between the two may date back to contemporary accounts; it is not clear which of the two was constructed first.