WorldCat, for books other libraries have and will send here for you via Interlibrary Loan (ILL).
Read the detailed tips on the Find Books page of this guide to most effectively use the catalog, WorldCat, and ILL.
Definitely search both:
America: History & Life or Historical Abstracts (depending on whether your topic deals with the USA/Canada or not) for discovering articles from the greatest number of history journals and for more search tools, including the Historical Period limiter.
JSTOR, for searching the full text of articles in the first issue up through, typically, 3-5 years ago from those journals in the JSTOR collections we have.