Your assignment requires you to use particular, credible newspapers. The New York Times, Washington Post, and Wall Street Journal are all available to search on the free web using Google. In fact, the Google search box that pops up with your results when you search for one of these by title often works better than the in-site search functions you may find on these publications' web sites.
However, on the free web, newspaper coverage often doesn't go back very far in history. These links are to newspapers that have different dates of coverage in different databases. The databases that provide the articles from these newspapers usually don't format them like newspaper web sites, but they contain articles that the newspapers published.