Looking for online original news articles from the late 1800s about American Imperialism.........?

(No encyclopedia articles!!!) School project--they are supposed to be primary sources, meaning from the time period, like a news column or essay written in the 1800s. I don't really consider what America did then as imperialism (What Europe was doing at the time was), but I still have to do the ignment. I presume the teacher is talking about annexing Puerto Rico and places like that.