This collection was compiled by the Oregon Historical Society Research Library from multiple sources, and consists of papers of or relating to Philip Foster, an early emigrant to Oregon. The collection includes papers both from Foster's early life in Maine and his life in Oregon. The materials are a mix of original documents and copies, including photocopies and microfilm.

The bulk of the collection consists of correspondence, business documents, records of the Eagle Creek Post Office and Clackamas School District No. 17, legal documents, land records, and government papers. The correspondence is primarily letters to Foster, seventeen of which are from Francis W. Pettygrove. Other correspondents include Forbes Barclay, William Barlow, George L. Curry, Francis Ermatinger, Joseph Lane, John McLoughlin, Joseph N. Prescott, Samuel R. Thurston, and Foster's relatives. Of note among the correspondence is a letter to Foster (Box 1, Folder 11), dated October 21, 1855, and signed by Asa Lovejoy and others; it lodges a complaint that Foster confiscated hunting firearms from Native individuals whom Lovejoy describes as friendly with Euro-Americans. Business records in the collection include receipts, bills, and several account books and ledgers. They relate to Foster's involvement with the Barlow Road, his business partnerships with Francis W. Pettygrove and Walter Pomeroy, his involvement with the Willamette Cattle Company, and his farmstead at Eagle Creek. Land, legal, and government documents include records relating to Foster's property and land claims by other Oregonians, contracts, and tax receipts. The legal papers include original court documents from the 1851 case Magruder v. Vanderpool (Box 4, Folder 6), which resulted in the expulsion of a man named Jacob Vanderpool from the Oregon Territory under the territory's Black exclusion laws, the only such expulsion on record. The collection also includes an account book that may have belonged to Foster's brother, Isaac; and a small amount of correspondence between Foster's relatives and other people.

In addition to Foster's papers, the collection contains a history of Eagle Creek and Clackamas School District No. 17 by E. L. Meyers; a biographical sketch of Foster and his family, accompanied by a 1960s inventory of the collection, with an addendum from 1975; and a book about the history of Penobscot County, Maine, with an inscription to Foster from his brother Herman N. Foster.