A primary source is an item that was created during the period being studied and documents in some way what is being studied.
Examples: Newspaper accounts, government documents, letters, diaries, autobiographies, speeches, oral histories, museum artifacts, photographs.
Seattle Taxicab Company Advertisement, 1911, from the University of Washington Digital Collections via Flickr Commons.
PSU and the summit Libraries has a large collection of reprinted or microfilmed primary source materials, including the collected writings of historical figures, government documents, diaries, collections of speeches, etc.
The best way to find primary sources in the library catalog is with subject headings. You may have to try several searches, but one strategy is to combine a keyword for your topic with a subject heading for a material type (see list below).
Subject headings relating to primary source material types:
I did the search above, and this book was the top result.
Due to cost, PSU Library will no longer be able to provide complete online access to the Oregonian articles published from 1987 - present.
The oregonlive.com web site provides free access to many Oregonian articles from the last few years, and supports fee-based article delivery of all Oregonian articles ($1.95 per article). The Multnomah County Public Library also provides full text access to the Oregonian.
An excellent library database for primary sources relevant to the Pacific Northwest.
Using a special collections library or archive is different from using public and academic libraries. For example, not all of the items in the collection may be cataloged, and you will probably not be able to browse the collection. The organization may have limited hours. There may rules around what you can bring into the reading area: some will allow only pencils and not pens, and you should plan to leave your food and drinks at home.
To prepare for your visit, explore the organization's website to see what collections they hold. Check the organization's hours. And then contact the organization to make an appointment, as not all archives are open without appointment.