The librarians at MNHS have created research guides for a number of different topics. If you're not sure what kind of resources they have in a particular area, this would be a good place to start. These guides also contain suggestions for secondary sources that you may be able to access through Carleton's library.
The online gateway to the MNHS's historical newspapers collection. Content older than 1922 can be accessed online, but newspapers more recent than that must be seen in person.