1966? Good. There was, in about 1967, the IBM 360/67 with 31 (up from the usual 24) bit addressing, virtual memory, and virtual machine software CP67 (Control Program 67) and interactive shell CMS (Conversational Monitor System).

Later of course, CP67/CMS became VM/CMS (Virtual Machine CMS) which was actually a big deal for IBM for decades if not to the present.

IIRC CP67/CMS was written at IBM's Cambridge Scientific Center, supposedly as a tool for operating system development. But by 1973, a company in Stamford, CT, NCSS (National CSS), was selling general purpose time-sharing service on 360/67 with CP67/CMS via just dial-up communications.

So, could log on and get ones own virtual machine, complete with a software command IPO (initial program load), the button on the front of the 360 machines. Then logged on could write and run assembler (made writing assembler surprisingly easy), PL/I, etc. If the software hit a bug with, say, an infinite loop, then could use IPO to start over!

NCSS service was popular around DC, and NCSS had an office in VA just over Key Bridge from DC with a leased phone line connection back to CT for a line printer. So, if wanted to print out a stack of paper 1" thick, could do that!

NCSS service was not cheap, but due to the Cold War and the Space Race there was plenty of money sloshing around DC for paying the NCSS bills.

IIRC in 1973 it was 6000 lines of typing in PL/I at NCSS that scheduled the fleet at FedEx, alleviated some concerns of the BoD, enabled some crucial funding, "Solved the most important problem facing the start of Federal Express" (COB F. Smith), and essentially saved the company (once of at least two times the company got saved).

By 1974, Brown University, especially its Division of Applied Mathematics, had a CP67/CMS system essentially donated by Tom Watson, Jr., who had gone to Brown. Brown instrumented the system to collect data on its operations. Statistician U. Grenander did a lot of statistical work with that data. He remarked, IRCC, that the data from the computer operations "looked nothing like biomedical data" he and statistics had long been used to.

And IBM's System/370 upgrade from System/360 had essentially all the 370/67 hardware features together with virtual machine assist that made some of the virtual machine faking faster.

Prime had an hierarchical file system in the 1970s, but as late as 1994 at IBM's Watson lab VM/CMS still didn't have hierarchies in the file system. As a partial alleviation, could have virtual disks, each with a drive letter.

Of course eventually the Multics ideas of authentication, capabilities, and access control lists made their way into IBM's RACF (Resource Access Control Facility) and much more generally in computing, e.g., with authentication via MIT's Kerberos with RSA (Rivest, Shamir, Adelman) public key encryption.

To me what is amazing are (i) a lot of concepts from those days are still with us, (ii) can buy, on-line, quantity 1, e.g., for about $100 an AMD FX-8350 processor with 8 cores, 64 bit addressing, and a standard clock speed of 4.0 GHz, (iii) can get at a small home office up/download Internet data rates of 1 Gbps for some reasonable price, say, $100 a month, and (iv) the early players IBM, GE, Honeywell, Prime, DEC, Data General, and more are no longer involved or are taking a back seat against QUALCOMM, Intel, AMD, Applied Materials, TSMC, Cisco, Microsoft, Apple, etc.