There's a strange assumption most people carry that the actual founding documents of the country exist somewhere behind glass, accessible only if you fly to D.C. and wait in a line. They do exist behind glass — but they're also just online, high-resolution, free, for anyone.
The National Archives and Records Administration is the federal government's official record-keeper, and its digitized holdings go far beyond the famous documents everyone already knows about. Yes, you can zoom into the actual Declaration of Independence, the Constitution, and the Bill of Rights. But the collection runs into the millions — presidential papers, treaties, military records, photographs, maps, and letters spanning the entire history of the country.
For genealogy research specifically, this is one of the best free resources that exists. Census records stretching back over a century, immigration and naturalization records, military service and pension files — all searchable, all free, no subscription required (unlike most commercial genealogy sites that gate this exact kind of record behind a paywall).
There's also a FOIA request portal if you're trying to obtain specific government records, presidential library archives for every administration, and educator resources built specifically for teaching directly from primary sources instead of textbook summaries.
It's not flashy. It's a government website, and it looks like one. But underneath that plain interface sits an almost absurd amount of actual, primary, unfiltered history — the kind you'd otherwise need a research trip and an appointment to access.
Go look at the real thing. It's been sitting there the whole time.