When historians talk about evidence, they often mean primary sources. Primary sources (diaries, letters, speeches, newspaper accounts, artifacts, etc. created during the time period being studied) can offer rich and unique insights into your topic. Thousands of primary documents have been digitized and can be found online on university, government and museum websites. The Bentley Library also has collections of these documents in printed source books.
A repository for digital collections. Items in the public domain (works published before 1923) are freely accessible online.