Historical New York Times:
Primary Resources in Search It:
Readers' Guide Retrospective: 1890-1982 = This database contains comprehensive indexing of the most popular general-interest magazines published in the United States.
AAS Historical Periodicals Collection = This database provides full-text access to a large collection of American periodicals published between 1684 and 1912.
U.S. Congressional Serial Set = Put your topic keyword(s) in the text box, you can change the "in Citation Text" pull-down select to "in Title" to narrow your search. Any topic relevant document you find in this database should be a primary source.
H. M. Stationery Service = This site has United Kingdom government documents dating back to the 13th century; be sure to use "advanced search" so you can restrict your exploration to particular historical time periods.
United Nations = This site has thousands of international government documents, but be aware that in terms of finding primary sources it is limited because the UN formed in 1945.
Financial Times Historical Archive, 1888- = likely the world's most well known business newspaper, covering the globe.
Here are resources that may be useful in finding non-documentary primary sources:
Search It = find historical primary sources with a search like this: your topic AND (diar* OR letter* OR interview*).
Academic Search Complete = Put your topic keyword(s) in the top text box, then put (diar* OR letter* OR interview* OR speech*) in the second box. You can change the "Select a Field (optional)" pull-down menu item to "TX All Text" to broaden your search as needed. Do not use newspaper, magazine or journal articles.
The Making of the Modern World = Contains over 62,000 titles from 1450-1914, you may want to limit to English, not all items might be considered primary sources so please check with your instructor/TA.
Collections of Primary Sources = Most of these collections provide primary sources for deeper historical coverage. The guide includes a link to the WSU Libraries' Manuscripts, Archive and Special Collections (MASC) department which features prominently the history of the Pacific Northwest. Explore the links in the Collections of Primary Sources and MASC websites to try to find a non-documentary primary source for your topic.
You may also find it possible to locate historical primary sources in the bibliographies of the articles and books you've previously collected. These are generally found at the end of the book/article, or included as footnotes.