Since 1951, the Benton County Historical Society has been preserving historical artifacts, photographs, and manuscripts. After Philomath citizens prevented the demolition of the 1867 Philomath College building and placed it on the National Register of Historic Places, The Society opened the building to the public in 1981 as a museum, research library and art gallery.

The Benton County Historical Museum artifact collection comprises approximately 66,000 items that illustrate the diverse themes of our Benton County, Oregon heritage. This extensive collection of Benton County related history materials includes 22,000 objects, maps, books, and documents, and approximately 44,000 images. Areas of collecting are based on local themes ranging from logging to technology to the arts, as well as specific topics such as Camp Adair, a World War II Military cantonment, and Philomath College, a United Brethren College that now houses the Museum.

In 2005, the Society accepted the responsibility of preserving the Horner Collection, formerly owned by Oregon State University. To house this vast collection and the Society's accumulation of important historical objects, the Society built a 13,500 square foot Collections Care Facility in 2007 on the Philomath campus for its growing collection of over 100,000 objects.