There are a ton of online collections displaying digitized materials! Finding them can be as simple as searching for "[topic] primary source" -- either using that exact phrasing, or substituting a specific type of primary source, e.g. "[topic] diary."
Many collections are hosted by a government entity like the Library of Congress as well as various universities. You can filter your search by specifying the site or its domain in your search. Use site:.gov for government results or .edu for university pages.
This version of the search limits not just to government sites but specifically Library of Congress results:
Evaluate your source's...
Is your source
Recent? Reliable? Relevant?
Is this source up-to-date? Is it about my topic, and does it go into enough depth? Does it come from an authoritative source? Is the information accurate (and are there citations given to back it up)? And why was this information written in the first place?