Settled prior to the American Civil War, the Town of Olla was originally known as Castor Sulfur Springs, with a steamboat port on Bayou Castor as its original site. In 1891, the Houston, Central Arkansas, and Northern Railroad came to what was then northwest Catahoula Parish and built its line more than a mile away from Castor Sulfur Springs. At that time, a new town was laid out and named for Olla Mills, a well educated, attractive, and accomplished young lady who was instrumental in community activities. The Town of Olla was officially incorporated on August 1, 1899, with Dr. William V. Taylor III as its first mayor. Olla was the site of the only documented train robbery in Louisiana, which occurred in August 1900. It became known for its excellent natural groundwater, leading to the Olla Bottling Works during the 1920s. The formation of the Olla State Bank in 1906 helped secure economic viability for the region, supporting area sawmill payrolls and surviving the Great Depression until its merger in the 1980s. The discovery of the Olla Oil Field in 1938 also fostered new growth and economic sustainability. Olla continues as a regional banking hub and is heavily involved with the forestry and petroleum production industries.