In this Library of Congress Blog post, read about the Library's latest iteration of its research guides. The new LibGuides are attractive and accessible, and each one includes an easy link to the Ask a Librarian service. Even if you do a Google search on a particular topic, such as 13th amendment, you're likely to see a link to guides.loc.gov early in the search results. That's a trick you could teach to students.
One example of a LibGuide that you could introduce to students is the one on Native American History and Culture: Finding Pictures. Here's a Carol Highsmith photo from my hometown that showed up on the first page of the LibGuide!
https://www.loc.gov/item/2015633463/
If you work with street law or even AP government teachers, you might want to refer them to the series of ten Beginner Guides built around law topics. Having trouble with your neighbors? Here's one example for you!
The blog post says you can propose topics for future LibGuides, too.