The collection contains bills and receipts, legal papers, business correspondence, sailor's agreements, financial statements, and personal estate papers of William B. Parker Jr. (1801-1878) from 1823 to 1854. The collection is arranged into two series.

Series I. Business Records contain records generated in the course of Parker Jr.'s career as a ship captain and maritime merchant. The materials document voyages from Salem to United States ports such as Boston, Charleston, New York, New Orleans, and San Francisco as well as international destinations, including Brazil, Cuba, France, Haiti, United Kingdom, Netherlands, Germany, and India. The materials also reference other captains or owners of vessels such as Isaac Cushing, John F. Andrew, William H. Caulfield, Richard S. Noble, Nathaniel Andrew, Thomas Aspinwall, and John Fairfield. While the primary language for the materials is English, some documents are written in Dutch, Italian, and Portuguese.

Series I is arranged into six subseries. The first four subseries, Mercator (Brig), Effort (Brig), Brazil (Bark), and Forrester (Ship), reflect the shipping vessel that was used when the records were created. These materials contain bills and receipts, which include lists of disbursements, price lists of goods from various ports, receipts for ship repairs and materials, and account deposits for deliveries at several international banks. The series also contains legal documents such as insurance claims; bills of sale for several ships; bills of lading; contracts and customs documents; correspondence about shipping requests or status updates from captains in Parker's employ; and Seamen's agreements. The bulk of the material is derived from the records of Brazil (Bark) and Forrester (Ship).

The fifth subseries, Other Vessels' Records, contain records from various other vessels Parker was associated with or may have been associated with. Many of the vessels represented in these materials only have one or two records in the collection. These records are similar in nature to the first four subseries and cover financial and legal materials with regard to these vessels' voyages. The sixth and final subseries, Baring Brothers & Co. Financial Records, includes correspondence and financial statements pertaining to Parker's accounts held with the Baring Brothers & Co. bank.

Series II. Personal Papers contains materials that were generated in the process of maintaining William B. Parker Jr.'s personal estate. It contains bill and receipts pertaining to repairs to the home, food deliveries, furniture purchases, and Parker's personal financial accounts and taxes.