The most notable portion of the collection relates to J. O. Simmons' time on the Mississippi River, with materials providing a detailed account of the Southern and Trans-Mississippi economy during the American Civil War and Reconstruction, including river commerce, the employment of African American and immigrant laborers, and political tensions between locals and economic opportunists who came down from Northern states.

Documents in this series specifically relate to J. O. Simmons' mercantile and agricultural business. Materials include correspondence, account books, bills of lading, bills of sale, invoices, receipts, permits, licenses, and various legal documents, such as money and land transfers, lease agreements, contracts, affidavits, and a lawsuit. These documents specifically relate to Simmons' enterprises in cotton farming, storekeeping, and provisioning businesses along the Mississippi River. It was in the course of these businesses that Simmons employed or sold goods to African American laborers, and these interactions are documented in agreements, account books, and legal documents.

For example, there are agreements between African American farm workers, various white property owners, and J. O. Simmons. In these documents, after crop payment was made for use of farmland, payment was also made to J. O. Simmons for "as much as becomes necessary to pay all of [the] store account," which refers to the nearby store that Simmons owned and operated. There are also agreements between Simmons and African American farm workers for use of his land at Amy Plantation.

There are papers which document a dispute between Gary Hood, the owner of the Black Bayou Plantation, and four African American farm workers to whom he had leased his land. In exchange for the cost of farming supplies and interest incurred, J. O. Simmons acted as the attorney for Phelon Dyer (sometimes referred to as Fielding or Dyer), Anthony Owens, Paul Jones, and William Gaiter who sought a settlement over this dispute. The dispute was over crops of cotton and corn the four men had farmed in 1865 and 1866 that they were never paid for, either by Gary Hood or the Bureau of Refugees, Freedmen, and Abandoned Lands.