Living Computer Museum
The Living Computer Museum (formal name Living Computers: Museum + Labs) is an institution in Seattle, Washington whose goal is to help people understand computing technology, particularly the historic computers which led to today's computers, by experiencing that actual, original, technology first-hand. Towards that goal, they proudly reckon to have "the world's largest collection of fully-restored - and useable - supercomputers, mainframes, minicomputers and microcomputers" (several of them one-of-a-kind survivors).
It was originally started by Paul Allen (one of the founders of Microsoft) in 1997, and opened to the public in 2012 (with its machines accessible both in person, at their facility, as well as remotely, over the Internet). It quickly grew into one of the two premier computer museums in the USA. After the death of Mr. Allen, and the start of the COVID pandemic, it has unfortunately suspended operations. Remote access remains open to the public.