The focus of the Plambeck Papers is Plambeck’s survey and research of various ethnic groups in Oregon. The collection contains documentation relating to the survey itself including completed questionnaires, correspondence, contact lists, progress reports, and notes from interviews. The papers also consist of reference materials that include newspaper clippings, event programs, article reprints, circulars, reports, photographs embedded within reports, student papers, and newspapers from various American ethnic communities. Most of the files are arranged by nationality or religious group.

The collection includes Plambeck’s project planning materials which he used to prepare for his ethnic studies research. These materials include lists of research topics, sources to consider when conducting the research, contact information, questionnaires, status of his research, and write ups of his findings and conclusions. Other types of documents within his planning materials include correspondence, notebooks, surveys, newspaper clippings, and pamphlets.

Plambeck’s ethnic groups research materials include student papers, notes, interview notes, personal correspondence, newspaper clippings, photographs embedded within reports, church pamphlets, and his own writings. These materials mainly cover ethnic groups in Oregon, but also other regions of the United States, including Minnesota, South Dakota, New York, and California. Most of the reference materials date from the 1940s through the 1950s, but the whole scope ranges from the 1900s to the 1990s. Several topics addressed in these materials include Japanese internment during World War II, discrimination against African Americans, immigration, cultural celebrations, and interracial marriage.

The student papers primarily represent assignments for coursework in "race relations" classes taught by William Smith at Linfield College and Texas Christian University. They discuss personal accounts of being first, second, and third generation immigrants in the United States for ethnic groups such as Irish, Norwegian, Jewish, Russian, Japanese, Hungarian, Mexican, Spanish, Korean, Filipino, French, Scandinavian, Finnish, Italian, Helvetia, etc. These race relations narratives are written by Oregonian students, but the papers pertain to the ethnic experience in the U.S. in general, often mixed with religious identities. The bulk of these papers were written between the 1920s and 1940s and contain several essays written by professor William Smith.